github.skymusic.top/tdewolff/minify
WARNING: an API change is happening soon, be aware or continue using the old API in tag v1.0.0
Minify is a minifier package written in Go. It has build-in HTML5, CSS3, JS, JSON, SVG and XML minifiers and provides an interface to implement any minifier. Minification is the process of removing bytes from a file (such as whitespace) without changing its output and therefore speeding up transmission over the internet. The implemented minifiers are high performance and streaming (which implies O(n)).
It associates minification functions with mime types, allowing embedded resources (like CSS or JS in HTML files) to be minified too. The user can add any mime-based implementation. Users can also implement a mime type using an external command (like the ClosureCompiler, UglifyCSS, ...). It is possible to pass parameters through the mimetype to specify the charset for example.
Bottleneck for minification is mainly io and can be significantly sped up by having the file loaded into memory and providing a Bytes() []byte function like bytes.Buffer does.
Table of Contents
Online live demo running on a Raspberry Pi 2.
Command-line-interface executable minify provided for tooling.
Roadmap
Minifiers or bindings to minifiers exist in almost all programming languages. Some implementations are merely using several regular-expressions to trim whitespace and comments (even though regex for parsing HTML/XML is ill-advised, for a good read see Regular Expressions: Now You Have Two Problems). Some implementations are much more profound, such as the YUI Compressor, Google Closure Compiler for JS and the HTML Compressor.
These industry-grade minifiers are written in Java and are generally relatively slow. Futhermore, these tools provide a large number of configurations which is often confusing or not required. Regular-expression based minifiers are slow anyways because they use multiple regular-expressions, each of which parses the complete document. While regular-expressions are overkill (or ill-advised) for parsing HTML/CSS/JS documents, parsing it a number of times is certainly not speeding things up. Other implementations are mostly written in uncompiled languages such as JS, which is great for bindings with Grunt for example, but catastrophic for the minification speed of large files or projects with many files.
Additionally, many of these minifier either do not follow the specifications or drag a lot of legacy code around. When you are still trying to support IE6 I don't suppose you are squeezing out every bit of performance from your web applications. Supporting old mistakes or work-arounds is not a fairly long-term vision and seldomly justified.
However, implementing an HTML minifier is the bare minimum. HTML documents can contain embedded resources such as CSS, JS and SVG file formats. Thus for increased minification of HTML, other file format minifiers must be present too. A minifier should really handle a number of mediatypes to be successful.
This minifier proves to be that fast and encompassing minifier which stream-minifies files and can minify them concurrently.
HTML (with JS and CSS) minification typically runs at about 35MB/s ~= 120GB/h, depending on the composition of the file.
| Website | Original | Minified | Ratio | Time* |
|---|---|---|---|---|
| Amazon | 463kB | 414kB | 89% | 13ms |
| BBC | 113kB | 96kB | 85% | 4ms |
| StackOverflow | 201kB | 182kB | 91% | 6ms |
| Wikipedia | 435kB | 410kB | 94%** | 12ms |
*These times are measured on my home computer which is an average development computer. The duration varies a lot but it's important to see it's in the 10ms range! The benchmark uses all the minifiers and excludes reading from and writing to the file from the measurement.
**Is already somewhat minified, so this doesn't reflect the full potential of this minifier.
HTML Compressor performs worse in output size (for HTML and CSS) and speed; it is a magnitude slower. Its whitespace removal is not precise or the user must provide the tags around which can be trimmed.
An alternative library written in Go is https://github.com/dchest/htmlmin. It is simpler but slower. Also https://github.com/omeid/jsmin contains a port of JSMin, just like this JS minifier, but is slower.
Other alternatives are bindings to existing minifiers written in other languages. These are inevitably more robust and tested but will often be slower. For example, Java-based minifiers incur overhead of starting up the JVM.
The HTML5 minifier uses these minifications:
html, head, body, ...)tr, td, li, ... and often p)http:, https: and javascript:)doctype and meta charsetAfter recent benchmarking and profiling it became really fast and minifies pages in the 10ms range, making it viable for on-the-fly minification.
However, be careful when doing on-the-fly minification. Minification typically trims off 10% and does this at worst around about 20MB/s. This means users have to download slower than 2MB/s to make on-the-fly minification worthwhile. This may or may not apply in your situation. Rather use caching!
The whitespace removal mechanism collapses all sequences of whitespace (spaces, newlines, tabs) to a single space. It trims all text parts (in between tags) depending on whether it was preceded by a space from a previous piece of text and whether it is followed up by a block element or an inline element. In the former case we can omit spaces while for inline elements whitespace has significance.
Make sure your HTML doesn't depend on whitespace between block elements that have been changed to inline or inline-block elements using CSS. Your layout should not depend on those whitespaces as the minifier will remove them. An example is a menu consisting of multiple <li> that have display:inline-block applied and have whitespace in between them. It is bad practise to rely on whitespace for element positioning anyways!
Minification typically runs at about 20MB/s ~= 70GB/h.
| Library | Original | Minified | Ratio | Time* |
|---|---|---|---|---|
| Bootstrap | 134kB | 111kB | 83% | 5ms |
| Gumby | 182kB | 167kB | 90% | 8ms |
*The benchmark excludes the time reading from and writing to a file from the measurement.
The CSS minifier will only use safe minifications:
margin, padding and border-width number of sides+ and zeros and rewriting with/without exponentrgb(, rgba(, hsl( and hsla( colors to hex or namenormal and bold by numbers for font-weight and fontnone → 0 for border, background and outlineIt does purposely not use the following techniques:
font-weight within an already existing font, too complex)!important)margin-top, margin-right, margin-bottom and margin-left → margin)body > div#elem p → #elem p)div[id=a] → div#a)It's great that so many other tools make comparison tables: CSS Minifier Comparison, CSS minifiers comparison and CleanCSS tests. From the last link, this CSS minifier is almost without doubt the fastest and has near-perfect minification rates. It falls short with the purposely not implemented and often unsafe techniques, so that's fine.
The JS minifier is pretty basic. It removes comments, whitespace and line breaks whenever it can. It employs all the rules that JSMin does too, but has additional improvements. For example the prefix-postfix bug is fixed.
Minification typically runs at about 40MB/s ~= 150GB/h. Common speeds of PHP and JS implementations are about 100-300kB/s (see Uglify2, Adventures in PHP web asset minimization).
| Library | Original | Minified | Ratio | Time* |
|---|---|---|---|---|
| ACE | 630kB | 442kB | 70% | 16ms |
| jQuery | 242kB | 130kB | 54% | 6ms |
| jQuery UI | 459kB | 300kB | 65% | 12ms |
| Moment | 97kB | 51kB | 52% | 2ms |
*The benchmark excludes the time reading from and writing to a file from the measurement.
TODO:
Minification typically runs at about 75MB/s ~= 270GB/h. It shaves off about 15% of filesize for common indented JSON such as generated by JSON Generator.
The JSON minifier only removes whitespace, which is the only thing that can be left out.
The SVG minifier uses these minifications:
doctype, XML prelude, metadatag, svg, ...)px unitpath data m attributeTODO:
rect, line, polygon, polyline to path
Minification typically runs at about 50MB/s ~= 180GB/h.
The XML minifier uses these minifications:
Run the following command
go get github.com/tdewolff/minify
or add the following imports and run the project with go get
import (
"github.com/tdewolff/minify"
"github.com/tdewolff/minify/css"
"github.com/tdewolff/minify/html"
"github.com/tdewolff/minify/js"
"github.com/tdewolff/minify/json"
"github.com/tdewolff/minify/svg"
"github.com/tdewolff/minify/xml"
)
Retrieve a minifier struct which holds a map of mediatype → minifier functions.
m := minify.New()
The following loads all provided minifiers.
m := minify.New()
m.AddFunc("text/css", css.Minify)
m.AddFunc("text/html", html.Minify)
m.AddFunc("text/javascript", js.Minify)
m.AddFunc("image/svg+xml", svg.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]json$"), json.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]xml$"), xml.Minify)
Minify from an io.Reader to an io.Writer for a specific mediatype.
if err := m.Minify(mediatype, w, r); err != nil {
panic(err)
}
Minify HTML, CSS or JS directly from an io.Reader to an io.Writer. The passed mediatype is not required for these functions, but are filled out for clarity.
if err := css.Minify(m, "text/css", w, r); err != nil {
panic(err)
}
if err := html.Minify(m, "text/html", w, r); err != nil {
panic(err)
}
if err := js.Minify(m, "text/javascript", w, r); err != nil {
panic(err)
}
if err := json.Minify(m, "application/json", w, r); err != nil {
panic(err)
}
if err := svg.Minify(m, "image/svg+xml", w, r); err != nil {
panic(err)
}
if err := xml.Minify(m, "text/xml", w, r); err != nil {
panic(err)
}
Minify from and to a []byte for a specific mediatype.
b, err = minify.Bytes(m, mediatype, b)
if err != nil {
panic(err)
}
Minify from and to a string for a specific mediatype.
s, err = minify.String(m, mediatype, s)
if err != nil {
panic(err)
}
Add a function for a specific mediatype.
m.AddFunc(mediatype, func(m minify.Minifier, mediatype string, w io.Writer, r io.Reader) error {
// ...
return nil
})
Add a command cmd with arguments args for a specific mediatype.
m.AddCmd(mediatype, exec.Command(cmd, args...))
Mediatypes can contain parameters (type/subtype; key1=val2; key2=val2). Minifiers can also be added using a regular expression. For example a minifier with image/.* will match any image mime.
Mediatypes such as text/plain; charset=UTF-8 will be processed by text/plain or any regexp it matches. The mediatype string is passed to the minifier function which can retrieve the parameters using the standard library mime.ParseMediaType.
Basic example that minifies from stdin to stdout and loads the default HTML, CSS and JS minifiers. Optionally, one can enable java -jar build/compiler.jar to run for JS (for example the ClosureCompiler). Note that reading the file into a buffer first and writing to a pre-allocated buffer would be faster (but would disable streaming).
package main
import (
"log"
"os"
"os/exec"
"github.com/tdewolff/minify"
"github.com/tdewolff/minify/css"
"github.com/tdewolff/minify/html"
"github.com/tdewolff/minify/js"
"github.com/tdewolff/minify/json"
"github.com/tdewolff/minify/svg"
"github.com/tdewolff/minify/xml"
)
func main() {
m := minify.New()
m.AddFunc("text/css", css.Minify)
m.AddFunc("text/html", html.Minify)
m.AddFunc("text/javascript", js.Minify)
m.AddFunc("image/svg+xml", svg.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]json$"), json.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]xml$"), xml.Minify)
// Or use the following for better minification of JS but lower speed:
// m.AddCmd("text/javascript", exec.Command("java", "-jar", "build/compiler.jar"))
if err := m.Minify("text/html", os.Stdout, os.Stdin); err != nil {
panic(err)
}
}
Custom minifier showing an example that implements the minifier function interface. Within a custom minifier, it is possible to call any minifier function (through m minify.Minifier) recursively when dealing with embedded resources.
package main
import (
"bufio"
"fmt"
"io"
"log"
"strings"
"github.com/tdewolff/minify"
)
func main() {
m := minify.New()
// remove newline and space bytes
m.AddFunc("text/plain", func(m minify.Minifier, mediatype string, w io.Writer, r io.Reader) error {
rb := bufio.NewReader(r)
for {
line, err := rb.ReadString('\n')
if err != nil && err != io.EOF {
return err
}
if _, errws := io.WriteString(w, strings.Replace(line, " ", "", -1)); errws != nil {
return errws
}
if err == io.EOF {
break
}
}
return nil
})
out, err := minify.String(m, "text/plain", "Because my coffee was too cold, I heated it in the microwave.")
if err != nil {
panic(err)
}
fmt.Println(out)
// Output: Becausemycoffeewastoocold,Iheateditinthemicrowave.
}
ResponseWriter example which returns a ResponseWriter that minifies the content and then writes to the original ResponseWriter. Any write after applying this filter will be minified.
type MinifyResponseWriter struct {
http.ResponseWriter
io.Writer
}
func (m MinifyResponseWriter) Write(b []byte) (int, error) {
return m.Writer.Write(b)
}
func MinifyFilter(res http.ResponseWriter, mimetype string) http.ResponseWriter {
m := minify.New()
// add other minfiers
pr, pw := io.Pipe()
go func(w io.Writer) {
if err := m.Minify(mimetype, w, pr); err != nil {
panic(err)
}
}(res)
return MinifyResponseWriter{res, pw}
}
Released under the MIT license.
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