minimizer-webpack-plugin
Advanced tools
This plugin minifies your assets in a webpack build. It ships with several
built-in minimizers covering JavaScript, JSON, HTML, CSS, and images — pick one
with the minify option and target the right files with
test.
JavaScript minimizers:
terser — MinimizerPlugin.terserMinify (default). The same JavaScript-based minifier that webpack uses out of the box; produces small, well-tested output and supports the full set of extractComments modes.uglify-js — MinimizerPlugin.uglifyJsMinify. ES5-only minifier, useful when you specifically need UglifyJS-compatible output. Requires npm install --save-dev uglify-js.@swc/core — MinimizerPlugin.swcMinify. A very fast Rust-based JavaScript/TypeScript minifier. Requires npm install --save-dev @swc/core.esbuild — MinimizerPlugin.esbuildMinify. An extremely fast JS bundler/minifier; legal comments are always preserved (no extractComments support). Requires npm install --save-dev esbuild.JSON minimizer:
JSON.stringify — MinimizerPlugin.jsonMinify. Built in (no extra dependency); supports space and replacer options.HTML minimizers:
webpack.html.syntax.htmlMinify. Ships with webpack (>= 5.111.0), so it needs no extra dependency, and it is the one that minifies what a document nests: an inline <style>, every style="", a <script>, an <svg> subtree. See webpack's own minimizers.html-minifier-terser — MinimizerPlugin.htmlMinifierTerser. JavaScript-based, no native dependency. Requires npm install --save-dev html-minifier-terser.@swc/html — MinimizerPlugin.swcMinifyHtml (full HTML documents) and MinimizerPlugin.swcMinifyHtmlFragment (HTML fragments, e.g. <template> content). Very fast Rust-based platform for the Web. Requires npm install --save-dev @swc/html.@minify-html/node — MinimizerPlugin.minifyHtmlNode. A Rust HTML minifier optimised for speed and effectiveness. Requires npm install --save-dev @minify-html/node.CSS minimizers:
webpack.css.syntax.cssMinify. Ships with webpack (>= 5.111.0), so it needs no extra dependency, and it minifies the CSS a stylesheet or a document nests. See webpack's own minimizers.cssnano — MinimizerPlugin.cssnanoMinify. Built on top of PostCSS. Requires npm install --save-dev cssnano postcss.csso — MinimizerPlugin.cssoMinify. A CSS minifier with structural optimisations. Requires npm install --save-dev csso.clean-css — MinimizerPlugin.cleanCssMinify. A widely-used CSS optimiser. Requires npm install --save-dev clean-css.esbuild — MinimizerPlugin.esbuildMinifyCss. Very fast CSS minification using esbuild's CSS loader. Requires npm install --save-dev esbuild.lightningcss — MinimizerPlugin.lightningCssMinify. A Rust-based CSS parser, transformer, and minifier. Requires npm install --save-dev lightningcss.@swc/css — MinimizerPlugin.swcMinifyCss. A very fast Rust-based CSS minifier. Requires npm install --save-dev @swc/css.Image minimizers:
sharp — MinimizerPlugin.sharpMinify. Re-encodes an image as the format its name already claims (avif, gif, heif, jp2, jpeg, png, tiff, webp), and can resize, rotate, flip, grayscale, blur or sharpen on the way — from the options or from the asset's own name. Requires npm install --save-dev sharp.svgo — MinimizerPlugin.svgoMinify. Minifies SVG, including an asset/inline SVG that no test can match. Requires npm install --save-dev svgo.imagemin — MinimizerPlugin.imageminMinify. Runs the imagemin plugins you name. Requires npm install --save-dev imagemin plus each plugin. Pair it with MinimizerPlugin.imageminGenerate under generate when a plugin converts the format, since only that can rename the asset.@napi-rs/image — MinimizerPlugin.napiRsImageMinify. Rust codecs with no system dependency; recompresses png losslessly with oxipng and jpeg with mozjpeg, and can resize, turn, mirror, grayscale, invert or blur on the way — from the options or from the asset's own name. Requires npm install --save-dev @napi-rs/image.These only minify — they never change an image's format or name; see Images.
All of the non-default minimizers are declared as optional peer
dependencies — install only the ones you actually use. One plugin instance
covers several languages at once: give minify an array and each
minimizer is offered only the assets its own filter accepts, so JS, CSS,
HTML and JSON share a single worker pool (see Examples).
Webpack v5 comes with the latest minimizer-webpack-plugin out of the box.
If you are using Webpack v5 or above and wish to customize the options, you will still need to install minimizer-webpack-plugin.
Using Webpack v4, you have to install terser-webpack-plugin v4 (minimizer-webpack-plugin is only published for Webpack v5+).
To begin, you'll need to install minimizer-webpack-plugin:
npm install minimizer-webpack-plugin --save-dev
or
yarn add -D minimizer-webpack-plugin
or
pnpm add -D minimizer-webpack-plugin
Then add the plugin to your webpack configuration. For example:
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [new MinimizerPlugin()],
},
};
Finally, run webpack using the method you normally use (e.g., via CLI or an npm script).
Works only with source-map, inline-source-map, hidden-source-map and nosources-source-map values for the devtool option.
Why?
eval wraps modules in eval("string") and the minimizer does not handle strings.cheap has no column information and the minimizer generates only a single line, which leaves only a single mapping.Using supported devtool values enable source map generation.
testincludeexcludeparallelminifyminimizerOptions (deprecated)generateextractCommentstestType:
type test = string | RegExp | (string | RegExp)[];
Default: /\.m?js(\?.*)?$/i
Test to match files against.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
test: /\.js(\?.*)?$/i,
}),
],
},
};
includeType:
type include = string | RegExp | (string | RegExp)[];
Default: undefined
Files to include.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
include: /\/includes/,
}),
],
},
};
excludeType:
type exclude = string | RegExp | (string | RegExp)[];
Default: undefined
Files to exclude.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
exclude: /\/excludes/,
}),
],
},
};
parallelType:
type parallel = boolean | number;
Default: true
Use multi-process parallel running to improve the build speed.
Default number of concurrent runs: os.cpus().length - 1 or os.availableParallelism() - 1 (if this function is supported).
Note
Parallelization can speedup your build significantly and is therefore highly recommended.
Warning
If you use Circle CI or any other environment that doesn't provide the real available count of CPUs then you need to explicitly set up the number of CPUs to avoid
Error: Call retries were exceeded(see #143, #202).
booleanEnable/disable multi-process parallel running.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
parallel: true,
}),
],
},
};
numberEnable multi-process parallel running and set number of concurrent runs.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
parallel: 4,
}),
],
},
};
minifyType:
type minifyFn = (
input: Record<string, string | Buffer>,
sourceMap: import("@jridgewell/trace-mapping").SourceMapInput | undefined,
minifyOptions: {
module?: boolean | undefined;
ecma?: import("terser").ECMA | undefined;
},
extractComments:
| boolean
| "all"
| "some"
| RegExp
| ((
astNode: any,
comment: {
value: string;
type: "comment1" | "comment2" | "comment3" | "comment4";
pos: number;
line: number;
col: number;
},
) => boolean)
| {
condition?:
| boolean
| "all"
| "some"
| RegExp
| ((
astNode: any,
comment: {
value: string;
type: "comment1" | "comment2" | "comment3" | "comment4";
pos: number;
line: number;
col: number;
},
) => boolean)
| undefined;
filename?: string | ((fileData: any) => string) | undefined;
banner?:
string | boolean | ((commentsFile: string) => string) | undefined;
}
| undefined,
) => Promise<{
code: string;
map?: import("@jridgewell/trace-mapping").SourceMapInput | undefined;
errors?: (string | Error)[] | undefined;
warnings?: (string | Error)[] | undefined;
extractedComments?: string[] | undefined;
}>;
interface minimizer {
implementation: minifyFn;
options?: Record<string, any>;
}
type minify = minifyFn | (minifyFn | minimizer)[] | minimizer;
Default: MinimizerPlugin.terserMinify
Which minimizer runs, and the options it runs with. By default the plugin uses terser; overriding it is also how you test an unpublished version or a fork.
Warning
Always use
requireinsideminifyfunction whenparalleloption enabled.
objectThe form to prefer: the minimizer and its own options in one place.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: MinimizerPlugin.swcMinify,
options: { mangle: false },
},
}),
],
},
};
options reaches the minify function as its third argument, and what it takes
is that minimizer's own: Terser's
minify options for the
default one, and the tables in
webpack's own minimizers for cssMinify and
htmlMinify.
filter(name, info) states which assets this minimizer is offered — return
false to decline one, and anything else (undefined included) to accept. It
answers for a filter property on the minimizer function itself, which is what
the built-ins carry, so setting it here is how you narrow one of them without
wrapping it.
new MinimizerPlugin({
minify: {
implementation: MinimizerPlugin.sharpMinify,
options: { encodeOptions: { jpeg: { quality: 80 } } },
filter: (name) => !name.includes("do-not-touch"),
},
});
Two keys are filled in before a minimizer sees them, and only when options
does not set them itself: ecma, from
output.environment,
and module, from the asset's own javascriptModule info or its .mjs /
.cjs extension. Setting either yourself wins, including module: false.
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: MinimizerPlugin.terserMinify,
options: {
ecma: undefined,
parse: {},
compress: {},
mangle: true, // Note `mangle.properties` is `false` by default.
module: false,
// Deprecated
output: null,
format: null,
toplevel: false,
nameCache: null,
ie8: false,
keep_classnames: undefined,
keep_fnames: false,
safari10: false,
},
},
}),
],
},
};
arraySeveral minimizers are an array of objects, rather than one object holding two
lists that have to line up. Each asset is dispatched to the minimizers whose
filter accepts it, and when more than one accepts the same asset the output
of each is fed to the next (the chain semantic). Warnings, errors and extracted
comments from all of them are merged.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: [
{
implementation: MinimizerPlugin.terserMinify,
options: { mangle: false },
},
{ implementation: MinimizerPlugin.swcMinify },
],
}),
],
},
};
Each entry carries its own filter as well as its own options, which is how
the same minimizer runs twice over different assets:
new MinimizerPlugin({
test: /\.(jpe?g|png)$/i,
minify: [
{
implementation: MinimizerPlugin.sharpMinify,
options: { encodeOptions: { jpeg: { quality: 60 } } },
filter: (name) => name.includes("thumb"),
},
{
implementation: MinimizerPlugin.sharpMinify,
options: { encodeOptions: { jpeg: { quality: 90 } } },
filter: (name) => !name.includes("thumb"),
},
],
});
This is also what lets one plugin instance and one worker pool handle every
asset type: each built-in ships with a filter matching its natural
extension, so JS, CSS, HTML and JSON need no second instance. test still
defaults to JS only, so widen it to let the other assets reach the dispatcher:
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
test: /\.(?:[cm]?js|css|html?|json)(\?.*)?$/i,
minify: [
{ implementation: MinimizerPlugin.terserMinify },
{ implementation: MinimizerPlugin.cssnanoMinify },
{ implementation: MinimizerPlugin.htmlMinifierTerser },
{ implementation: MinimizerPlugin.jsonMinify },
],
}),
],
},
};
Pair it with webpack's own cssMinify and
htmlMinify and the source a document or a stylesheet nests inside itself is
minified too — see Embedded source.
functionA bare function is shorthand for an object with no options. A custom one
says what it can do through properties on the function itself — each optional,
and each answering a question the plugin would otherwise have to guess at.
webpack.config.js
// Can be async
const minify = (input, sourceMap, minimizerOptions, extractsComments) => {
// Whatever the `minify` option's `options` holds reaches the third argument
// You can use `minimizerOptions.myCustomOption`
// Custom logic for extract comments
const { map, code } = require("uglify-module") // Or require('./path/to/uglify-module')
.minify(input, {/* Your options for minification */});
return { map, code, warnings: [], errors: [], extractedComments: [] };
};
// Used to regenerate `fullhash`/`chunkhash` between different implementation
// Example: you fix a bug in custom minimizer/custom function, but unfortunately webpack doesn't know about it, so you will get the same fullhash/chunkhash
// to avoid this you can provide version of your custom minimizer
// You don't need if you use only `contenthash`
minify.getMinimizerVersion = () => {
let packageJson;
try {
packageJson = require("uglify-module/package.json");
} catch (error) {
// Ignore
}
return packageJson && packageJson.version;
};
// Restrict the minimizer to the assets it can actually handle. The plugin
// skips assets for which `filter` returns `false` and (when an array of
// minimizers is used) dispatches each asset only to the minimizers that
// accept it. Returning `undefined` is treated as accept.
minify.filter = (name) => /\.[cm]?js(\?.*)?$/i.test(name);
// The languages this minimizer minifies. Source a module embeds in another
// language carries no filename, so `filter` cannot dispatch it and this does
// — a function without it is never handed any.
minify.getTypes = () => ["javascript"];
// Declare this when the minimizer reads the asset's bytes rather than its
// text — an image minimizer. Its `input` values then arrive as a `Buffer` and
// its `code` may be one. Only applied when every minimizer an asset is
// dispatched to declares it, since one that does not could not read the bytes.
minify.supportsBinary = () => true;
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: minify,
options: { myCustomOption: true },
},
}),
],
},
};
A minifier that nests other languages inside what it prints — a document
with an inline <style>, a stylesheet with a data: URL — hands each nested
body out instead of minifying it itself. It declares which languages it can
offer, and the plugin passes renderEmbeddedSource in its options when
something else claims one of them:
async function myHtmlMinify(input, sourceMap, minimizerOptions) {
const [[, code]] = Object.entries(input);
const { renderEmbeddedSource } = minimizerOptions;
// Absent when nothing configured claims a language this minifier offers
const minifyStyle = async (css) => {
const result = renderEmbeddedSource
? await renderEmbeddedSource(css, { type: "css" })
: undefined;
// Declining leaves the body exactly as it was written
return result && typeof result.code === "string" ? result.code : css;
};
return { code: await print(code, minifyStyle) };
}
// The languages this minifier can hand out, given the options it will run with
myHtmlMinify.getEmbeddedTypes = (minimizerOptions) => ["css", "javascript"];
renderEmbeddedSource(source, { type, as }) answers
{ code?, warnings?, errors? } or undefined, and recurses — a body that
nests something of its own is reached too. as says which production of
type the body is; a style="" is "block-contents" rather than a whole
stylesheet. Embedded source has the whole picture.
minimizerOptionsNote
Deprecated, and to be removed in the next major release. Give a minimizer its options in
minifyinstead, which keeps one minimizer's configuration in one place. It keeps working, and setting the options for one minimizer in both places is an error.
Type:
type minimizerOptions = Record<string, any> | Record<string, any>[];
Default: Terser's
Options for the active minimizer, given away from it. With an array of minimizers it may be an array too — each element goes to the minimizer at the same index — or one object every minimizer is handed. It is still the only way to configure the default minimizer without naming it:
module.exports = {
optimization: {
minimize: true,
minimizer: [new MinimizerPlugin({ minimizerOptions: { mangle: false } })],
},
};
terserOptions is a deprecated alias of it — passing either is equivalent, and
minimizerOptions wins if both are set.
generateType:
type generateFn = (
input: Record<string, string | Buffer>,
sourceMap: undefined,
generatorOptions: Record<string, any>,
) => Promise<{
code: string | Buffer;
filename?: string;
errors?: (Error | string)[];
warnings?: (Error | string)[];
}>;
interface generator {
implementation: generateFn;
options?: Record<string, any>;
type?: "import" | "asset";
filename?: string;
filter?: (name: string) => boolean;
deleteOriginalAssets?: boolean;
}
type generate =
| generateFn
| generateFn[]
| generator
| Record<string, generateFn | generateFn[] | generator>;
Default: undefined
Rewrites a module's own bytes as it is built, rather than an asset after
the build. That is the one point at which a re-encoding can also rename —
return a filename and the asset is emitted under it, with every reference in
the bundle following. minify cannot: an asset's name is decided
during code generation, so renaming there would leave the bundle pointing at a
URL nothing emits.
test, include and exclude select which
modules it sees, matched against the module's resource — query and all, so
?as=webp is matchable. A generator runs in the webpack process, since
modules build before the worker pool is up, and its answer is cached under the
bytes plus the generator and its options.
Two generators ship with the plugin, and they differ in who picks the format.
sharpGenerate is told: it takes the target from the request's ?as= or,
failing that, from an options.encodeOptions naming exactly one format, and reports an error when neither says which format
to write. imageminGenerate is not: its plugins decide, so it reads the format
back off the bytes they produced and renames to match, leaving an asset its
plugins did not convert under the name it had.
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
module: {
rules: [
{
test: /\.(jpe?g|png)$/i,
type: "asset/resource",
// The query has to survive into the name, or two formats of one image
// collide.
generator: { filename: "[name][ext][query]" },
},
],
},
plugins: [
new MinimizerPlugin({
test: /\.(jpe?g|png)$/i,
generate: MinimizerPlugin.sharpGenerate,
}),
],
};
// `image.jpg` is emitted as `image.webp`, and this import points at it.
import webp from "./image.jpg?as=webp";
Written as an object, generate names its generators, and an asset picks
one by name with ?as=:
new MinimizerPlugin({
test: /\.(jpe?g|png)$/i,
generate: {
webp: {
implementation: MinimizerPlugin.sharpGenerate,
options: { encodeOptions: { webp: { quality: 90 } } },
},
avif: {
implementation: MinimizerPlugin.sharpGenerate,
options: { encodeOptions: { avif: { quality: 50 } } },
},
},
});
// And `./image.jpg?as=avif` for the other one.
import webp from "./image.jpg?as=webp";
A module naming no preset is left alone, so the same build can import an image unconverted. One naming a preset nothing defines is an error rather than a silent decline, since the name it asked for is what the bundle would point at.
A generator can also be written as an object — on its own, or under a name — which is where its own options live and what lets it read what was emitted instead of a module as it builds:
new MinimizerPlugin({
test: /\.(jpe?g|png)$/i,
generate: {
webp: {
implementation: MinimizerPlugin.sharpGenerate,
options: { encodeOptions: { webp: {} } },
type: "asset",
// Optional. Without it the generator's own name for the result is used,
// which for `sharpGenerate` is the original with its extension replaced.
filename: "[path][name].webp",
// Optional. Narrows what this generator reads, on top of `test`.
filter: (name) => !name.includes("icons/"),
// Optional, `false` by default: the asset it read stays where it is.
deleteOriginalAssets: false,
},
},
});
type decides which of the two things a generator does, and they are not
interchangeable — they read different input, at different points in the build:
"import" (the default) | "asset" | |
|---|---|---|
| Reads | a module, as it builds | an asset, once it is emitted |
| Produces | that module's own bytes, renamed with them | a new file beside the one it read |
| Picked by | ?as=<name> on the import | test / include / exclude, then filter |
| Reaches a file nothing imports | no | yes — copied assets included |
| Fields it reads | implementation, options | those plus filename, filter, deleteOriginalAssets |
| webpack | 5.111 or newer | any supported version |
"import" is the only point at which a rename can reach the bundle: the
asset is named while its module is built, so every reference follows it. The
import that asked for the conversion gets the converted file.
new MinimizerPlugin({
test: /\.(jpe?g|png)$/i,
generate: { webp: { implementation: MinimizerPlugin.sharpGenerate } },
});
import url from "./photo.jpg?as=webp"; // url is "photo.webp"
const same = new URL("./photo.jpg?as=webp", import.meta.url); // photo.webp
.hero {
background: url("./photo.jpg?as=webp"); /* photo.webp */
}
photo.webp the jpg became this
Those are one asset module between them, so an import, a new URL() and a
CSS url() all follow the rename. An asset inlined as a data URI carries no
file name, and takes the media type of what it became — data:image/webp;….
"asset" leaves what it read alone and writes another file next to it, so
both survive — the <picture> case, where the .webp goes in a srcset you
write yourself and the .jpg stays as the fallback. Nothing imports the new
file, so ?as= cannot reach it and its preset name selects nothing; the name
is only how you address its options. An asset already generated is never
generated from again.
new MinimizerPlugin({
test: /\.(jpe?g|png)$/i,
generate: {
webp: { implementation: MinimizerPlugin.sharpGenerate, type: "asset" },
},
});
import url from "./photo.jpg"; // url is "photo.jpg", unchanged
photo.jpg still there, unless `deleteOriginalAssets`
photo.webp generated beside it
filename, filter and deleteOriginalAssets describe a file being written
beside another, so they belong to "asset" and setting one on an "import"
generator is an error rather than a field that quietly does nothing.
ecma is filled in from
output.environment
unless a generator's options set it, the same way it is for a minimizer's —
see minify.
filename is a
webpack filename template
resolved against the asset read, so [path], [name], [base], [ext] and
[query] are available; content hashes are not, because the name derives from
one the original already carries.
In watch mode the rename is carried on the module rather than reapplied each build, so a rebuild that does not touch the image keeps pointing at the generated name without running the generator again. Changing the image does run it again, since its answer is cached under the bytes.
The same holds across runs under
cache.type: "filesystem",
where a module is restored from the pack rather than rebuilt. That restored
result is the generator's, so changing a generator or its options has to
invalidate the pack, and the plugin adds their identity to
cache.version so
it does. This needs the plugin to be in the config — plugins or
optimization.minimizer — since webpack builds the cache while it applies
them; a plugin applied by hand after webpack() returns is too late to reach
it, and a changed generator would then be ignored until the cache directory is
removed.
Note
Note
generatorOptionsis kept as a deprecated way of giving a generator its options — one object for one generator, an array positionally matching an array of them, or keyed by name wheregeneratenames its generators. Prefer a generator's ownoptions. Setting both for one generator is an error, and a key naming no generator is an error rather than silently doing nothing.
Note
An
"import"generator needs a webpack whoseNormalModuleprocessResulthook can be awaited (5.111 or newer), since that is where a rename has to happen. On an older webpack the plugin reports an error rather than silently generating nothing. An"asset"generator does not use that hook and works on any supported webpack.
extractCommentsType:
type extractComments =
| boolean
| string
| RegExp
| ((
astNode: any,
comment: {
value: string;
type: "comment1" | "comment2" | "comment3" | "comment4";
pos: number;
line: number;
col: number;
},
) => boolean)
| {
condition?:
| boolean
| "all"
| "some"
| RegExp
| ((
astNode: any,
comment: {
value: string;
type: "comment1" | "comment2" | "comment3" | "comment4";
pos: number;
line: number;
col: number;
},
) => boolean)
| undefined;
filename?: string | ((fileData: any) => string) | undefined;
banner?:
string | boolean | ((commentsFile: string) => string) | undefined;
};
Default: true
Whether comments shall be extracted to a separate file, (see details).
By default, extract only comments using /^\**!|@preserve|@license|@cc_on/i RegExp condition and remove remaining comments.
If the original file is named foo.js, then the comments will be stored to foo.js.LICENSE.txt.
A minimizer's options.format.comments specifies whether the comment will be preserved - i.e., it is possible to preserve some comments (e.g. annotations) while extracting others, or even preserve comments that have already been extracted.
booleanEnable/disable extracting comments.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
extractComments: true,
}),
],
},
};
stringExtract all or some (use the /^\**!|@preserve|@license|@cc_on/i RegExp) comments.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
extractComments: "all",
}),
],
},
};
RegExpAll comments that match the given expression will be extracted to a separate file.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
extractComments: /@extract/i,
}),
],
},
};
functionAll comments that match the given expression will be extracted to a separate file.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
extractComments: (astNode, comment) => {
if (/@extract/i.test(comment.value)) {
return true;
}
return false;
},
}),
],
},
};
objectAllows you to customize condition for extracting comments, and specify the extracted file name and banner.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
extractComments: {
condition: /^\**!|@preserve|@license|@cc_on/i,
filename: (fileData) =>
// The "fileData" argument contains object with "filename", "basename", "query" and "hash"
`${fileData.filename}.LICENSE.txt${fileData.query}`,
banner: (licenseFile) =>
`License information can be found in ${licenseFile}`,
},
}),
],
},
};
conditionType:
type condition =
| boolean
| "all"
| "some"
| RegExp
| ((
astNode: any,
comment: {
value: string;
type: "comment1" | "comment2" | "comment3" | "comment4";
pos: number;
line: number;
col: number;
},
) => boolean)
| undefined;
The condition that determines which comments should be extracted.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
extractComments: {
condition: "some",
filename: (fileData) =>
// The "fileData" argument contains object with "filename", "basename", "query" and "hash"
`${fileData.filename}.LICENSE.txt${fileData.query}`,
banner: (licenseFile) =>
`License information can be found in ${licenseFile}`,
},
}),
],
},
};
filenameType:
type filename = string | ((fileData: any) => string) | undefined;
Default: [file].LICENSE.txt[query]
Available placeholders: [file], [query] and [filebase] ([base] for webpack 5).
The file where the extracted comments will be stored.
Default is to append the suffix .LICENSE.txt to the original filename.
Warning
We highly recommend using the
.txtextension. Using.js/.cjs/.mjsextensions may conflict with existing assets, which leads to broken code.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
extractComments: {
condition: /^\**!|@preserve|@license|@cc_on/i,
filename: "extracted-comments.js",
banner: (licenseFile) =>
`License information can be found in ${licenseFile}`,
},
}),
],
},
};
bannerType:
type banner = string | boolean | ((commentsFile: string) => string) | undefined;
Default: /*! For license information please see ${commentsFile} */
The banner text that points to the extracted file and will be added at the top of the original file.
It can be false (no banner), a String, or a function<(string) -> String> that will be called with the filename where the extracted comments have been stored.
The banner will be wrapped in a comment.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
extractComments: {
condition: true,
filename: (fileData) =>
// The "fileData" argument contains object with "filename", "basename", "query" and "hash"
`${fileData.filename}.LICENSE.txt${fileData.query}`,
banner: (commentsFile) =>
`My custom banner about license information ${commentsFile}`,
},
}),
],
},
};
Source written in one language that reaches the bundle inside another is
minified too, which no asset carries and an asset-level minimizer therefore
never sees. It needs no option (webpack >= 5.110.0; older versions reach only
what an asset nests inside itself).
Such source has no filename, so test / include / exclude and each
minimizer's filter — all of which match filenames — cannot dispatch it.
It is dispatched by the language it is written in, which every minify
function states for itself:
myCssMinifier.getTypes = () => ["css"];
webpack's own cssMinify and htmlMinify declare css and html, and are
the two that hand out what they nest. The built-ins declare javascript
(terserMinify, uglifyJsMinify, swcMinify, esbuildMinify), css
(cssnanoMinify, cssoMinify, cleanCssMinify, esbuildMinifyCss,
lightningCssMinify, swcMinifyCss), html (htmlMinifierTerser,
swcMinifyHtml, swcMinifyHtmlFragment, minifyHtmlNode) and json
(jsonMinify). A language no configured minimizer
claims — svg out of the box — is emitted exactly as it was written, and a
custom minify function without getTypes is never handed embedded source at
all.
What this reaches:
exportType but link).asset/source module embeds, and the payload an asset/inline
module encodes — the payload before it is encoded, so the encoding covers
what came back. A language written as text only: an inline svg is
offered, an inline png or jpeg is not, so a raster image that becomes a
data: URI is minified by generate rather than here.<style>,
every style="", a <script> holding JavaScript or JSON, an <svg> subtree,
the document an <iframe srcdoc> holds, and the payload of a url() data:
URL. This is how an inline <script> is minified by terser at all.A style="" arrives as css with as: "block-contents" — the same word
module.parser.css.as uses. It holds a block's contents rather than a whole
stylesheet, so a minifier claiming css is handed one either way and as says
which it is. Ignore it at your peril: parsing a declaration list as a stylesheet
finds no rule and returns nothing.
A <script type="module"> arrives the same way, as javascript with
as: "module": JavaScript has two productions too, and a module script is one
wherever it sits. The built-in JavaScript minimizers read it as their own
module option, so the engine is never handed the word itself; a minify
function of your own claiming javascript is handed it and decides. Ignore it
at your peril: a module script read as a classic one is a syntax error the
moment it holds a top-level await.
An event handler attribute — onclick="" — arrives as javascript with
as: "event-handler": its value is a function body, the production the
return cancelling an event is written in. No JavaScript engine here parses one
on its own, so each built-in minimizer minifies the function that body belongs
to and answers with the body back out of it. A minify function of your own is
handed the body as written and reads it however its engine can.
The nested case needs a minifier that can hand its nested bodies out, which it
also states for itself — webpack's cssMinify and htmlMinify do:
// The languages this minifier can offer, given the options it will run with.
myHtmlMinifier.getEmbeddedTypes = (minimizerOptions) => ["css", "javascript"];
The option is passed only when the two declarations meet: if nothing configured claims a language this minifier could offer, it is never handed one, and minification is exactly what it always was. When it is, the nested bodies are reached in the same parse that prints — the minifier leaves a marker where each one goes and the answers are put in their place, so nothing is parsed twice.
Note
Source a module embeds in JavaScript is minified during code generation, before the worker pool is up, so
paralleldoes not apply to it. What an asset nests inside itself is minified in the pool with the asset.
Extract all legal comments (i.e. /^\**!|@preserve|@license|@cc_on/i) and preserve /@license/i comments.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: MinimizerPlugin.terserMinify,
options: { format: { comments: /@license/i } },
},
extractComments: true,
}),
],
},
};
If you want to build without comments, use this config:
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: MinimizerPlugin.terserMinify,
options: { format: { comments: false } },
},
extractComments: false,
}),
],
},
};
uglify-jsUglifyJS is a JavaScript parser, minifier, compressor and beautifier toolkit.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: MinimizerPlugin.uglifyJsMinify,
// `options` will be passed to `uglify-js`
// Link to options - https://github.com/mishoo/UglifyJS#minify-options
options: {},
},
}),
],
},
};
swcswc is a super-fast compiler written in Rust, producing widely supported JavaScript from modern standards and TypeScript.
Warning
extractCommentsis supported with@swc/core >= 1.15.30. Only serializable extract conditions are supported: booleans,"some","all", string patterns,RegExpvalues without flags, or object conditions that resolve to those forms. Function conditions and flagged regular expressions are not supported.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: MinimizerPlugin.swcMinify,
// `options` will be passed to `swc` (`@swc/core`)
// Link to options - https://swc.rs/docs/config-js-minify
options: {},
},
}),
],
},
};
esbuildesbuild is an extremely fast JavaScript bundler and minifier.
Warning
The
extractCommentsoption is not supported, and all legal comments (i.e. copyright, licenses and etc) will be preserved.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: MinimizerPlugin.esbuildMinify,
// `options` will be passed to `esbuild`
// Link to options - https://esbuild.github.io/api/#minify
// Note: the `minify` options is true by default (and override other `minify*` options), so if you want to disable the `minifyIdentifiers` option (or other `minify*` options) please use:
// options: {
// minify: false,
// minifyWhitespace: true,
// minifyIdentifiers: false,
// minifySyntax: true,
// },
options: {},
},
}),
],
},
};
Uses JSON.stringify() to minify your JSON files during the build process.
webpack.config.js
module.exports = {
optimization: {
minimize: true,
minimizer: [
// Keeps original terser plugin to minify JS files
"...",
// Will minify JSON files (they can come from copy-webpack-plugin or when you are using asset modules)
new MinimizerPlugin({
test: /\.json$/,
minify: {
implementation: MinimizerPlugin.jsonMinify,
// We are supporting `space` and `replacer` options, you can set them below
options: {},
},
}),
],
},
};
The plugin can minify HTML assets too. Pick one of the bundled HTML
minimizers and set test to match your HTML files.
Available HTML minimizers:
webpack.html.syntax.htmlMinify — webpack's own, shipped with webpack itself, so it needs no extra dependency. The one that can minify what a document nests — an inline <style>, a <script>, an <svg>. See webpack's own minimizers.MinimizerPlugin.htmlMinifierTerser — uses html-minifier-terser.MinimizerPlugin.swcMinifyHtml — uses @swc/html for full HTML documents (with doctype and <html>/<head>/<body> tags).MinimizerPlugin.swcMinifyHtmlFragment — uses @swc/html for HTML fragments (e.g. content inside <template></template> or partial HTML strings).MinimizerPlugin.minifyHtmlNode — uses @minify-html/node.The HTML minimizers are optional peer dependencies — install only the one you actually use:
npm install --save-dev html-minifier-terser
# or
npm install --save-dev @swc/html
# or
npm install --save-dev @minify-html/node
Note
HTML assets typically come from plugins like
copy-webpack-plugin,html-webpack-plugin, or webpack's asset modules.
Note
Whitespace handling differs between tools (defaults):
@swc/html— removes/collapses whitespace only in safe places (aroundhtml/body, inside<head>, between<meta>/<script>/<link>etc.).html-minifier-terser— always collapses multiple whitespaces to a single space (never removes entirely); configurable via its options.@minify-html/node— see its whitespace docs.
html-minifier-terserhtml-minifier-terser is a JavaScript-based HTML minifier with no native dependency.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
// Keeps the default Terser plugin for JS files
"...",
new MinimizerPlugin({
test: /\.html(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.htmlMinifierTerser,
// Options - https://github.com/terser/html-minifier-terser#options-quick-reference
options: {
collapseWhitespace: true,
removeComments: true,
},
},
}),
],
},
};
@swc/html — HTML documentsUse swcMinifyHtml for complete HTML documents (i.e. with a doctype and <html>/<head>/<body> tags).
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.html(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.swcMinifyHtml,
// Options - https://github.com/swc-project/bindings/blob/main/packages/html/index.ts
options: {},
},
}),
],
},
};
@swc/html — HTML fragmentsUse swcMinifyHtmlFragment for partial HTML — for example, content of <template></template> tags or HTML strings that get injected into another document.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.template\.html$/i,
minify: {
implementation: MinimizerPlugin.swcMinifyHtmlFragment,
// Options - https://github.com/swc-project/bindings/blob/main/packages/html/index.ts
options: {},
},
}),
],
},
};
Note
The difference between
swcMinifyHtmlandswcMinifyHtmlFragmentis the error reporting — invalid or broken syntax is reported at build time.
@minify-html/node@minify-html/node is a Rust HTML minifier.
webpack.config.js
const Minimizer = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new Minimizer({
test: /\.html(\?.*)?$/i,
minify: {
implementation: Minimizer.minifyHtmlNode,
// Options - https://github.com/wilsonzlin/minify-html#minification
options: {},
},
}),
],
},
};
You can also stack multiple MinimizerPlugin instances to compress different files with different minify functions in the same build (e.g. JS with terserMinify, HTML with htmlMinifierTerser, JSON with jsonMinify).
The plugin can minify CSS assets too. Pick one of the bundled CSS
minimizers and set test to match your CSS files.
Available CSS minimizers:
webpack.css.syntax.cssMinify — webpack's own, shipped with webpack itself, so it needs no extra dependency. The one that can minify the CSS a document nests. See webpack's own minimizers.MinimizerPlugin.cssnanoMinify — uses cssnano (via postcss).MinimizerPlugin.cssoMinify — uses csso.MinimizerPlugin.cleanCssMinify — uses clean-css.MinimizerPlugin.esbuildMinifyCss — uses esbuild with the CSS loader.MinimizerPlugin.lightningCssMinify — uses lightningcss.MinimizerPlugin.swcMinifyCss — uses @swc/css.The CSS minimizers are optional peer dependencies — install only the ones you actually use:
npm install --save-dev cssnano postcss
# or
npm install --save-dev csso
# or
npm install --save-dev clean-css
# or
npm install --save-dev esbuild
# or
npm install --save-dev lightningcss
# or
npm install --save-dev @swc/css
Note
CSS assets typically come from plugins like
mini-css-extract-pluginor webpack's asset modules.
cssnanocssnano runs as a PostCSS plugin.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
// Keeps the default Terser plugin for JS files
"...",
new MinimizerPlugin({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.cssnanoMinify,
// Options - https://cssnano.github.io/cssnano/docs/config-file/
options: {
preset: "default",
},
},
}),
],
},
};
cssocsso is a CSS minifier with structural optimisations.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.cssoMinify,
// Options - https://github.com/css/csso#minifysource-options
options: {},
},
}),
],
},
};
clean-cssclean-css is a widely-used CSS optimiser.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.cleanCssMinify,
// Options - https://github.com/clean-css/clean-css#constructor-options
options: {},
},
}),
],
},
};
esbuildesbuild ships with a fast CSS minifier (used via its CSS loader).
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.esbuildMinifyCss,
// Options - https://esbuild.github.io/api/#transform-api
options: {},
},
}),
],
},
};
lightningcsslightningcss is a Rust-based CSS parser, transformer, and minifier.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.lightningCssMinify,
// Options - https://lightningcss.dev/transpilation.html
options: {},
},
}),
],
},
};
@swc/css@swc/css is a Rust-based CSS minifier.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.swcMinifyCss,
// Options - https://github.com/swc-project/bindings/blob/main/packages/css/index.ts
options: {},
},
}),
],
},
};
webpack ships a CSS and an HTML minimizer of its own. They need no extra
dependency — if you have webpack, you have them — and they are the two that
can hand out what a document or a stylesheet nests inside itself, so pairing
them with terserMinify and jsonMinify is what minifies embedded source
(see Embedded source). They are reached through webpack's
public css.syntax and html.syntax exports, and need webpack 5.111.0 or
newer.
const MinimizerPlugin = require("minimizer-webpack-plugin");
const { cssMinify } = require("webpack").css.syntax;
const { htmlMinify } = require("webpack").html.syntax;
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
test: /\.(?:[cm]?js|css|html|json)(\?.*)?$/i,
minify: [
{ implementation: MinimizerPlugin.terserMinify },
{ implementation: cssMinify },
{ implementation: htmlMinify },
{ implementation: MinimizerPlugin.jsonMinify },
],
}),
],
},
};
Each one dispatches itself, so test only has to be wide enough to let the
assets through: cssMinify claims *.css and htmlMinify claims *.html
through their own filter, and both run in the worker pool.
cssMinify | htmlMinify | |
|---|---|---|
getTypes() | css | html |
getEmbeddedTypes() | svg, css, html, json, javascript | css, javascript, json, svg, html |
filter | /\.css(\?.*)?$/i | /\.html(\?.*)?$/i |
supportsWorkerThreads() | true | true |
Their options are optimization.minimize.css and
optimization.minimize.html respectively. environment carries what the
target can read ({ browsers, vendorPrefixes }, the CSS entries of
output.environment),
so a spelling the target could not parse is never reached for.
cssMinify optionsEvery option is named directly on the object — the per-transform switches sit beside the rest, not nested.
| Option | Type | Default | What it does |
|---|---|---|---|
environment | { browsers?: string[], vendorPrefixes?: boolean } | — | What the target can read. browsers is a browserslist selection; vendorPrefixes: false leaves prefixes alone. |
as | "stylesheet" | "block-contents" | "stylesheet" | Which production to read the source as. The plugin sets it — a style="" arrives as "block-contents". |
convertLengthUnits | boolean | false | Rewrite a length into a shorter unit it is exactly equal in (16px → 1pc). Off because it earns nothing once compressed. |
rewriteCustomProperties | boolean | false | Shorten a custom property's value like any other (--x:#ffffff → --x:#fff). Off because getPropertyValue() hands that text back. |
unusedSymbols | string[] | — | Names a whole-project analysis found unused; a bare name is a class, id or @keyframes, a ---prefixed one a custom property. |
pseudoClasses | { [name: string]: string } | — | Write a pseudo-class as a class instead, so a script can apply it where the engine does not. |
renderEmbeddedSource | function | — | Owned by the plugin — do not pass it. |
Per-transform switches, each on unless set to false:
| Switch | What it rewrites |
|---|---|
colorFallbacks | Writes a color the target cannot read as an extra declaration before it, in a spelling it does read. |
lowerUnsupported | Writes a spelling the target cannot read as one it can — the same value, said another way. |
foldCase | Lowercases a name that matches ASCII case-insensitively (at-rule, property, pseudo, function, unit, keyword). |
rewriteEscapes | Writes an escaped identifier the shortest way that names it. |
comments | Which comments survive: "some" (default), true / "all", false, or a pattern / predicate over the comment's text. |
resolveCustomAtRules | Inlines what @custom-media / @custom-selector names, and drops the rule that named it. |
mergeLonghands | Writes a family of longhands as the one shorthand that sets them. |
mergeRules | Joins rules printing the same block, at-rules sharing a prelude, and a @layer block a later sibling reopens. |
normalizeQuotes | Normalizes quoting of strings, url(), font families and attribute values. |
reduceFunctions | Computes a call into the shorter call naming the same value (calc(), transforms, gradients, easings, filters). |
removeDeadRules | Drops a rule or declaration nothing can read — an empty rule, one an identical later one supersedes. |
rewriteDirSelector | Writes a :dir() the target cannot read as the [dir] attribute selector. |
shortenColors | Writes each color in the shortest spelling of the same value. |
shortenMediaQueries | Writes a media feature in its range spelling and collapses an and of two into the interval. |
shortenNumbers | Writes each number in its shortest equal spelling. |
shortenSelectors | Rewrites a selector into a shorter equal one. |
shortenValues | Writes a value the shortest way its property's own grammar allows. |
htmlMinify options| Option | Type | Default | What it does |
|---|---|---|---|
environment | same as cssMinify | — | CSS's, not HTML's: handed to the CSS minifier this runs over inline CSS. |
css | object | {} | The CSS minifier's options for that inline CSS — see below. |
collapseWhitespace | boolean | "conservative" | "smart" | "all" | false | Collapses each run of whitespace in text, except where an ancestor renders it verbatim; "smart" also drops what sits against a block edge, "all" every edge. |
removeEmptyAttributes | boolean | false | Drops an attribute whose empty value leaves it in the state its absence gives. |
removeEmptyElements | boolean | false | Drops an element with no children and no attributes, unless its bare form is meaningful. |
mergeStyles | boolean | false | Prints a run of adjacent <style> elements as one sheet. |
sortAttributes | boolean | false | Prints attributes commonest name first, ties by name — nothing in HTML reads the order. |
sortTokenLists | boolean | false | Prints every token list the DOM reads as a set (class, rel, part, …) in token order. |
removeRedundantAttributes | boolean | "smart" | "all" | false | Drops an attribute whose value is the element's own default; "all" also drops spec defaults a selector can match. |
removeImpliedTags | boolean | "smart" | "all" | "smart" | How much of the <html> / <head> / <body> shell may be left out: "smart" only the <html> start tag, true / "all" all six. |
minifyConditionalComments | boolean | false | Minifies the markup inside a conditional comment's body. |
renderEmbeddedSource | function | — | Owned by the plugin — do not pass it. |
Per-transform switches, each on unless set to false:
| Switch | What it rewrites |
|---|---|
collapseBooleanAttributes | Writes a boolean attribute spelled with its own name (disabled="disabled") as the bare name. |
comments | Which comments survive — same values as CSS's. One a parser or server reads is kept regardless. |
normalizeAttributeQuotes | Drops or re-picks an attribute value's quotes. |
normalizeEnumeratedAttributes | Folds an enumerated value to the keyword it names. |
normalizeListAttributes | Normalizes a space-, comma- or descriptor-separated list (class, rel, srcset, sizes, viewport content). |
normalizeNumericAttributes | Writes an integer attribute the one way its rules read it. |
removeOptionalTags | Leaves out an optional tag other than the shell, which is removeImpliedTags. |
The css object takes the CSS minifier's convertLengthUnits,
rewriteCustomProperties, unusedSymbols and pseudoClasses, plus the CSS
per-transform switches. environment is not among them: htmlMinify runs
the CSS minifier over every inline <style> and style="", so environment
stays top level, shared by the document and the CSS inside it. Give the two
minimizers the same environment and a .css asset and the same declaration
inline agree about the target:
const environment = { browsers: ["chrome 100", "safari 15"] };
const options = [
{},
// cssMinify
{ environment, convertLengthUnits: true },
// htmlMinify — `environment` reaches the CSS it nests; `css` carries the rest
{ environment, css: { convertLengthUnits: true } },
{},
];
Note
Do not pass
renderEmbeddedSourceyourself. The plugin owns that option: it wires the minimizers to each other with it, and a value you set is replaced. What a minimizer offers and what another claims is what routes embedded source — see Embedded source.
Both minimizers re-resolve webpack when they run, in the worker pool as well
as in the main process, so the webpack resolvable from this plugin has to be
the one they came from, and at least 5.111.0 — the release that exports them
on webpack.css.syntax and webpack.html.syntax. On an older webpack the
destructure above yields undefined; a second or older copy in the tree
surfaces from inside the minifier as:
Cannot destructure property 'SourceProcessor' of 'webpack.css.syntax' as it is undefined.
Cannot destructure property 'askEmbeddedRenderer' of 'webpack.html.syntax' as it is undefined.
Deduplicate webpack (npm dedupe, or a single version in a workspace root) and
it goes away.
The plugin can minify image assets too. Pick one of the bundled image
minimizers and set test to match your images.
Available image minimizers:
MinimizerPlugin.sharpMinify — uses sharp, re-encoding each image as its own format.MinimizerPlugin.svgoMinify — uses svgo.MinimizerPlugin.imageminMinify — uses imagemin and the plugins you name.MinimizerPlugin.napiRsImageMinify — uses @napi-rs/image, which ships prebuilt codecs.Converting an image to another format is generate's job rather
than a minimizer's, since only that can rename the asset:
MinimizerPlugin.sharpGenerate and MinimizerPlugin.imageminGenerate.
The image minimizers are optional peer dependencies — install only the ones you actually use:
npm install --save-dev sharp
# or
npm install --save-dev svgo
# or
npm install --save-dev imagemin imagemin-mozjpeg imagemin-pngquant
Note
On
minifythese only minify — they never change an image's format or name. An asset's name is decided during code generation, long before a minimizer runs, so a renamed asset would leave the bundle pointing at a URL nothing emits. Converting.pngto.webpis whatgenerateis for: it runs while the module builds, early enough to rename.
Note
sharpandimageminread the asset's bytes rather than its text, so they run in the webpack process rather than in the worker pool — they do their own threading. Minimizers configured beside them keep the pool.
minify runs over emitted assets, so an image that becomes a data: URI
instead of a file — asset/inline, or asset under
Rule.parser.dataUrlCondition
— never reaches it. An SVG is the exception, since it is text and webpack
offers it as embedded source.
Put the same minimizer under generate and it does reach one: a
generator runs while the module builds, over the bytes themselves, before
anything encodes them. It renames nothing unless it answers with a name, so a
minimizer stays a minimizer there.
new MinimizerPlugin({
test: /\.(jpe?g|png)$/i,
generate: { implementation: MinimizerPlugin.sharpMinify },
});
Do not list the same image minimizer in both for the same assets — an emitted
one would then be re-encoded twice, which costs time and, for a lossy format,
quality. generate covers inlined and emitted images alike; minify is the
one to keep when nothing is inlined, since it runs after the whole build and
caches per asset. An "import" generator needs webpack 5.111 or newer.
Images are optimized in one of two modes:
Which one you get with no encodeOptions at all, measured by decoding the
output back to pixels and comparing it with the input:
| Format | sharpMinify | napiRsImageMinify |
|---|---|---|
avif | lossy | lossy |
gif | lossy | not handled |
jpeg | lossy | lossless |
png | lossless | lossless |
tiff | lossy | not handled |
webp | lossy | lossy |
So sharpMinify is lossy by default everywhere except PNG — it re-encodes at
sharp's own defaults, which are quality settings rather than lossless ones.
napiRsImageMinify is lossless by default for both PNG and JPEG, because those
two are repacked in place by oxipng and mozjpeg, rewriting the encoded bytes
rather than decoding to pixels and encoding again.
svgoMinify rewrites markup rather than pixels. It is lossless in the sense
that the rendered image is meant to be unchanged, but its default plugin preset
does rewrite paths and drop metadata — see
svgo for which of those to turn
off.
imageminMinify is whatever its plugins are. imagemin-jpegtran,
imagemin-optipng and imagemin-gifsicle are lossless; imagemin-mozjpeg and
imagemin-pngquant are lossy. imagemin-svgo can be either.
Asking sharpMinify for lossless output
new MinimizerPlugin({
test: /\.(png|jpe?g|webp|avif)(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.sharpMinify,
options: {
encodeOptions: {
// https://sharp.pixelplumbing.com/api-output
jpeg: { quality: 100 },
webp: { lossless: true },
avif: { lossless: true },
// PNG is already lossless at sharp's defaults
png: {},
},
},
},
});
Asking napiRsImageMinify for lossy output, which is where the savings are:
new MinimizerPlugin({
test: /\.(png|jpe?g|webp|avif)(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.napiRsImageMinify,
options: {
encodeOptions: {
// Anything below 100 re-encodes rather than repacking
jpeg: { quality: 80 },
webp: { quality: 80 },
avif: { quality: 70 },
// `png` has no quality setting — it is lossless either way
},
},
},
});
Note
Lossless does not mean "no smaller". On this repository's own PNG fixture
napiRsImageMinifyreturns 59% of the original size without touching a single pixel, andsharpMinifyreturns 92%.
sharpsharp re-encodes each image as the format
its name already claims, so a .png stays a PNG. It handles avif, gif,
heif, jp2, jpeg, png, tiff and webp.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
// Keeps the default Terser plugin for JS files
"...",
new MinimizerPlugin({
test: /\.(png|jpe?g|webp|avif|tiff?|gif)$/i,
minify: {
implementation: MinimizerPlugin.sharpMinify,
options: {
// Options are keyed by sharp's format name
// https://sharp.pixelplumbing.com/api-output
encodeOptions: {
jpeg: { quality: 80 },
png: { compressionLevel: 9 },
webp: { lossless: true },
},
},
},
}),
],
},
};
sharp can also transform the image while it re-encodes:
new MinimizerPlugin({
test: /\.(png|jpe?g)$/i,
minify: {
implementation: MinimizerPlugin.sharpMinify,
options: {
// `enabled` and `unit` ("px" by default, or "percent") are read here;
// everything else goes to sharp
// https://sharp.pixelplumbing.com/api-resize
resize: { width: 800, unit: "px", fit: "inside" },
// A number of degrees, or "auto" to follow the EXIF orientation
rotate: "auto",
flip: false,
flop: false,
grayscale: false,
// A sigma, or true for a fast default
blur: false,
sharpen: false,
encodeOptions: { jpeg: { quality: 80 } },
},
},
});
Each of these can also be asked for by an asset's own name — see Query strings in asset names.
svgosvgo minifies SVG. It also reaches an
asset/inline SVG — one that becomes a data: URI rather than a file — which
carries no asset name for test to match; see
Embedded source.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.svg(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.svgoMinify,
options: {
// Options - https://github.com/svg/svgo#configuration
encodeOptions: {
multipass: true,
plugins: ["preset-default"],
},
},
},
}),
],
},
};
imageminimagemin runs the plugins you name.
Each is a string — "mozjpeg" resolves imagemin-mozjpeg — or a
[name, options] pair. Install each plugin yourself.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.(png|jpe?g|gif|svg)$/i,
minify: {
implementation: MinimizerPlugin.imageminMinify,
options: {
plugins: [
"gifsicle",
"mozjpeg",
["pngquant", { quality: [0.6, 0.8] }],
"svgo",
],
},
},
}),
],
},
};
Note
A plugin that converts —
imagemin-webp,imagemin-avif— writes a format the asset's name does not claim.imageminMinifykeeps the original and warns instead of writing it, since it cannot rename the asset. Reach forgeneratewithMinimizerPlugin.imageminGenerateto convert: it runs the same plugins while the module builds, which is where the asset can still take the name of the format they wrote.
@napi-rs/image@napi-rs/image is a set of Rust
codecs shipped as prebuilt binaries, so it needs no system library. It handles
avif, jpeg, png and webp — the formats it both reads back reliably and
makes smaller.
Each format is re-encoded as itself, using the codec that does that best:
png goes through oxipng, which
rewrites the container losslessly and leaves the pixels untouched, and jpeg
through mozjpeg. Decoding either to
pixels and re-encoding saves a small fraction as much.
webpack.config.js
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
"...",
new MinimizerPlugin({
test: /\.(png|jpe?g|webp|avif)$/i,
minify: {
implementation: MinimizerPlugin.napiRsImageMinify,
options: {
// Options are keyed by the format's own name
// https://github.com/Brooooooklyn/Image#usage
encodeOptions: {
// `PNGLosslessOptions`
png: { force: true },
// `JpegCompressOptions`
jpeg: { quality: 80 },
// `AvifConfig`
avif: { quality: 70, speed: 4 },
// The quality factor, 0-100
webp: { quality: 80 },
},
},
},
}),
],
},
};
Note
pngis recompressed losslessly, so it takes no quality setting. Resizing and rotating are not exposed here — usesharpfor those.
An asset keeps the query and fragment of the request that made it:
output.assetModuleFilename is [hash][ext][query][fragment] by default, so
import icon from "./icon.svg?v=2" is emitted as <hash>.svg?v=2.
test, include and exclude are read against both spellings — the whole name
and the name with the query and fragment stripped — so all three of these accept
that asset:
test: /\.svg$/i; // names the file
test: /\.svg(\?.*)?$/i; // names the query form
test: /\?v=2$/; // names the query itself
exclude rejects on either spelling, so excluding by file name also excludes
the queried asset. Every built-in minimizer's own filter reads past the query
in the same way.
Asking sharp for something from the import. sharpMinify reads what to do
off the asset's name, so one image can be sized, turned or re-encoded where it
is imported rather than in the configuration:
import banner from "./banner.png?width=320&quality=80";
| Query | Short | Value | What it does |
|---|---|---|---|
width | w | pixels, or auto | target width |
height | h | pixels, or auto | target height |
unit | u | px (default) or percent | how width and height are read |
fit | cover (default), contain, fill, … | what to do when both dimensions are given | |
position | pos | centre (default), right top, entropy, … | where to crop from |
background | bg | a colour | what contain pads with |
without-enlargement | flag | never scale the image up | |
rotate | rot | degrees, or auto | turn by an angle, or by the EXIF orientation |
flip | flag | mirror vertically | |
flop | flag | mirror horizontally | |
grayscale | gray | flag | drop the colour |
blur | sigma, or flag | blur | |
sharpen | sigma, or flag | sharpen | |
quality | q | a number | encode quality |
lossless | flag | encode losslessly, where the format has one | |
effort | a number | how hard the encoder tries | |
progressive | prog | flag | interlace, where the format has it |
| Import | What comes out |
|---|---|
./photo.jpg?w=64&h=64&fit=cover&pos=entropy | a 64x64 thumbnail, cropped to the busiest part |
./photo.jpg?width=16&blur&quality=30 | a tiny blurred placeholder |
./logo.png?width=50&unit=percent&grayscale | half-size and grey |
A flag is on when it is present — ?flip — and reads true/1/yes the
same way, false/0/no the other. greyscale and grey spell grayscale,
auto on width or height drops one set in the minimizer's options, and a
parameter can be spelled in any case.
Every one of these can also be set in the minimizer's options; the name wins where
both say something, being the more specific of the two. resize: { enabled: false } still turns resizing off entirely.
Two rules decide what happens to a value:
?v=2 must not become a
resize — and neither does ?width=nonsense or ?flip=maybe.effort runs to 6 for webp and 9 for avif, quality
starts at 0 for png and 1 for jpeg, and a colour is whatever it can parse. A
value outside those fails the build with sharp's own message rather than being
dropped silently. An option a format has no use for — ?lossless on a jpeg —
is simply ignored.napiRsImageMinify reads the same names, as far as @napi-rs/image goes:
width/w, height/h, fit (cover, fill, inside), filter
(nearest, triangle, catmull-rom, gaussian, lanczos3), rotate/rot,
flip, flop, grayscale, invert, blur, quality/q, lossless and
speed. Three differences are worth knowing:
rotate takes a quarter turn, not any angle — 90, 180, 270, a
negative or a multiple of those, or auto for the EXIF orientation. napi
applies one orientation, so mirroring and a turn compose into it (?flip&flop
is a half turn); asking for auto alongside an explicit turn warns, because
only one of them can be applied.fit without naming it, and answers a quality of
150 by silently writing a bigger file, so a value it would mishandle is
dropped instead.?rotate=auto on an image whose EXIF
asks for nothing skips the decode entirely.svgoMinify reads precision (or floatPrecision, 0–10), multipass,
pretty and indent, so one SVG can be laid out readably or coarsened
without a second configuration:
import icon from "./icon.svg?precision=1";
imageminMinify reads nothing. Its options are a list of already-configured
plugins, each with option names of its own, so there is no parameter a query
could set that would mean the same thing twice over.
Note
Two assets whose names differ only by their query would be written to the same file, and webpack refuses that. To emit several sizes of one image, give each its own file name and keep the query on the asset name:
module.exports = { output: { assetModuleFilename: (pathData) => { const query = pathData.module.resourceResolveData.query || ""; const name = query.replace(/^\?/, "-").replace(/[=&]/g, "-"); return `[name]${name}[ext][query]`; }, }, };Without the trailing
[query]the size is no longer on the name and nothing resizes; without the first half the two sizes collide.
Note
A query cannot pick a format on this path. Resizing needs no new name, which is why it works here; changing the format does, and
minifyruns after names are decided. Hand?as=webptogenerateinstead, which sees the module as it builds and can emit the new format under a new name.
minify takes an array, and each minimizer is offered only the assets its own
filter accepts, so one plugin instance can cover several languages at once:
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
test: /\.(js|css|svg|png|jpe?g)$/i,
minify: [
{ implementation: MinimizerPlugin.terserMinify },
{ implementation: MinimizerPlugin.cssnanoMinify },
{ implementation: MinimizerPlugin.svgoMinify },
{
implementation: MinimizerPlugin.sharpMinify,
options: { encodeOptions: { png: { compressionLevel: 9 } } },
},
],
}),
],
},
};
Override the default minify function - use uglify-js for minification.
webpack.config.js
const minifyWithUglifyJs = (file, sourceMap, minimizerOptions) => {
const uglifyJsOptions = { ...minimizerOptions };
// The plugin fills these two in, and `uglify-js` rejects options it does not know
delete uglifyJsOptions.ecma;
delete uglifyJsOptions.module;
if (sourceMap) {
uglifyJsOptions.sourceMap = { content: sourceMap };
}
return require("uglify-js").minify(file, uglifyJsOptions);
};
// Which assets it is offered, and which language it minifies. Without
// `getTypes` it is never handed the JavaScript a document or a module embeds
minifyWithUglifyJs.filter = (name) => /\.[cm]?js(\?.*)?$/i.test(name);
minifyWithUglifyJs.getTypes = () => ["javascript"];
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: minifyWithUglifyJs,
// https://github.com/mishoo/UglifyJS2#minify-options
options: {/* your `uglify-js` package options */},
},
}),
],
},
};
A minifier that nests other languages inside its own output hands each body
out with renderEmbeddedSource rather than minifying it itself — see
minify and Embedded source.
With default Terser minify function:
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
minify: {
implementation: MinimizerPlugin.terserMinify,
options: { compress: true },
},
}),
],
},
};
With built-in minify functions:
import { type JsMinifyOptions as SwcOptions } from "@swc/core";
import { type MinifyOptions as SwcCssOptions } from "@swc/css";
import {
type FragmentOptions as SwcHtmlFragmentOptions,
type Options as SwcHtmlOptions,
} from "@swc/html";
import { type OptionsOutput as CleanCssOptions } from "clean-css";
import { type Options as CssnanoOptions } from "cssnano";
import { type CompressOptions as CssoOptions } from "csso";
import { type TransformOptions as EsbuildOptions } from "esbuild";
import { type Options as HtmlMinifierTerserOptions } from "html-minifier-terser";
import { type TransformOptions as LightningCssOptions } from "lightningcss";
import { type MinifyOptions as TerserOptions } from "terser";
import { type MinifyOptions as UglifyJSOptions } from "uglify-js";
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin<SwcOptions>({
minify: {
implementation: MinimizerPlugin.swcMinify,
options: {
// `swc` options
},
},
}),
new MinimizerPlugin<UglifyJSOptions>({
minify: {
implementation: MinimizerPlugin.uglifyJsMinify,
options: {
// `uglif-js` options
},
},
}),
new MinimizerPlugin<EsbuildOptions>({
minify: {
implementation: MinimizerPlugin.esbuildMinify,
options: {
// `esbuild` options
},
},
}),
// Alternative usage:
new MinimizerPlugin<TerserOptions>({
minify: {
implementation: MinimizerPlugin.terserMinify,
options: {
// `terser` options
},
},
}),
// HTML minimizers
new MinimizerPlugin<HtmlMinifierTerserOptions>({
test: /\.html(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.htmlMinifierTerser,
options: {
// `html-minifier-terser` options
},
},
}),
new MinimizerPlugin<SwcHtmlOptions>({
test: /\.html(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.swcMinifyHtml,
options: {
// `@swc/html` options
},
},
}),
new MinimizerPlugin<SwcHtmlFragmentOptions>({
test: /\.template\.html$/i,
minify: {
implementation: MinimizerPlugin.swcMinifyHtmlFragment,
options: {
// `@swc/html` fragment options
},
},
}),
// CSS minimizers
new MinimizerPlugin<CssnanoOptions>({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.cssnanoMinify,
options: {
// `cssnano` options
},
},
}),
new MinimizerPlugin<CssoOptions>({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.cssoMinify,
options: {
// `csso` options
},
},
}),
new MinimizerPlugin<CleanCssOptions>({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.cleanCssMinify,
options: {
// `clean-css` options
},
},
}),
new MinimizerPlugin<EsbuildOptions>({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.esbuildMinifyCss,
options: {
// `esbuild` options (CSS loader)
},
},
}),
new MinimizerPlugin<LightningCssOptions>({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.lightningCssMinify,
options: {
// `lightningcss` options
},
},
}),
new MinimizerPlugin<SwcCssOptions>({
test: /\.css(\?.*)?$/i,
minify: {
implementation: MinimizerPlugin.swcMinifyCss,
options: {
// `@swc/css` options
},
},
}),
],
},
};
image-minimizer-webpack-pluginThis plugin does what
image-minimizer-webpack-plugin
did, for every asset type rather than images alone, so one plugin covers a
build instead of two. The options line up like this:
image-minimizer-webpack-plugin | here |
|---|---|
minimizer | minify, same shape |
minimizer.implementation | implementation on that minimizer |
minimizer.options | options on that minimizer |
minimizer.filter | a filter on the minimizer itself |
generator[].implementation | generate |
generator[].options | options on that generator |
generator[].preset | the key the generator is written under |
generator[].type | type on that generator |
generator[].filename / .filter | filename / filter on that generator |
deleteOriginalAssets | deleteOriginalAssets on that generator |
concurrency | parallel |
test / include / exclude | unchanged |
loader | nothing — generate reaches a module without one |
severityError | nothing — a failed minimizer is an error |
The minimizers and generators keep their names —
imageminMinify, imageminGenerate, imageminNormalizeConfig, sharpMinify,
sharpGenerate, svgoMinify — so only the plugin they are read off changes.
squooshMinify and squooshGenerate are not carried over: @squoosh/lib is
unmaintained, and image-minimizer-webpack-plugin already marked both
deprecated.
A minimizer carries over as it is written: minimizer becomes
minify, with the same { implementation, options } object, and an
array of them stays an array.
Before
const ImageMinimizerPlugin = require("image-minimizer-webpack-plugin");
module.exports = {
plugins: [
new ImageMinimizerPlugin({
test: /\.(jpe?g|png)$/i,
minimizer: {
implementation: ImageMinimizerPlugin.sharpMinify,
options: { encodeOptions: { jpeg: { quality: 80 } } },
},
}),
],
};
After
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
optimization: {
minimize: true,
minimizer: [
new MinimizerPlugin({
test: /\.(jpe?g|png)$/i,
minify: {
implementation: MinimizerPlugin.sharpMinify,
options: { encodeOptions: { jpeg: { quality: 80 } } },
},
}),
],
},
};
A generator is where two shapes changed rather than moved. Generators are
named here instead of listed, because a name is what ?as= asks for, so an
array of two generators becomes an object of two entries. And a generator that
produced a file beside the original is written with type: "asset", which is
the default there and not here — without it a generator re-encodes the module
itself, which is what lets the import be renamed.
Before
const ImageMinimizerPlugin = require("image-minimizer-webpack-plugin");
module.exports = {
plugins: [
new ImageMinimizerPlugin({
test: /\.(jpe?g|png)$/i,
generator: [
{
type: "asset",
preset: "webp",
implementation: ImageMinimizerPlugin.sharpGenerate,
options: { encodeOptions: { webp: { quality: 90 } } },
},
],
}),
],
};
After
const MinimizerPlugin = require("minimizer-webpack-plugin");
module.exports = {
plugins: [
new MinimizerPlugin({
test: /\.(jpe?g|png)$/i,
generate: {
webp: {
type: "asset",
implementation: MinimizerPlugin.sharpGenerate,
options: { encodeOptions: { webp: { quality: 90 } } },
},
},
}),
],
};
We welcome all contributions! If you're new here, please take a moment to review our contributing guidelines before submitting issues or pull requests.
FAQs
Minimizer plugin for webpack
The npm package minimizer-webpack-plugin receives a total of 7,027,567 weekly downloads. As such, minimizer-webpack-plugin popularity was classified as popular.
We found that minimizer-webpack-plugin demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 6 open source maintainers collaborating on the project.
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