github.com/lpha/minify
Online demo if you need to minify files now.
Command line tool that minifies concurrently and supports watching file changes.
All releases for various platforms.
Minify is a minifier package written in Go. It provides HTML5, CSS3, JS, JSON, SVG and XML minifiers and an interface to implement any other minifier. Minification is the process of removing bytes from a file (such as whitespace) without changing its output and therefore shrinking its size and speeding up transmission over the internet and possibly parsing. The implemented minifiers are designed for high performance.
The core functionality associates mimetypes with minification functions, allowing embedded resources (like CSS or JS within HTML files) to be minified as well. Users can add new implementations that are triggered based on a mimetype (or pattern), or redirect to an external command (like ClosureCompiler, UglifyCSS, ...).
compress)?gofmt for Go files?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 and Google Closure Compiler for JS. As most existing implementations either use JavaScript, use regexes, and don't focus on performance, they are pretty slow.
This minifier proves to be that fast and extensive minifier that can handle HTML and any other filetype it may contain (CSS, JS, ...). It is usually orders of magnitude faster than existing minifiers.
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"
)
There is no guarantee for absolute stability, but I take issues and bugs seriously and don't take API changes lightly. The library will be maintained in a compatible way unless vital bugs prevent me from doing so. There has been one API change after v1 which added options support and I took the opportunity to push through some more API clean up as well. There are no plans whatsoever for future API changes.
For all subpackages and the imported parse and buffer packages, test coverage of 100% is pursued. Besides full coverage, the minifiers are fuzz tested using github.com/dvyukov/go-fuzz, see the wiki for the most important bugs found by fuzz testing. Furthermore am I working on adding visual testing to ensure that minification doesn't change anything visually. By using the WebKit browser to render the original and minified pages we can check whether any pixel is different.
These tests ensure that everything works as intended, the code does not crash (whatever the input) and that it doesn't change the final result visually. If you still encounter a bug, please report here!
The benchmarks directory contains a number of standardized samples used to compare performance between changes. To give an indication of the speed of this library, I've ran the tests on my Thinkpad T460 (i5-6300U quad-core 2.4GHz running Arch Linux) using Go 1.9.2.
name time/op
CSS/sample_bootstrap.css-4 2.26ms ± 0%
CSS/sample_gumby.css-4 2.92ms ± 1%
HTML/sample_amazon.html-4 2.33ms ± 2%
HTML/sample_bbc.html-4 1.02ms ± 1%
HTML/sample_blogpost.html-4 171µs ± 2%
HTML/sample_es6.html-4 14.5ms ± 0%
HTML/sample_stackoverflow.html-4 2.41ms ± 1%
HTML/sample_wikipedia.html-4 4.76ms ± 0%
JS/sample_ace.js-4 7.41ms ± 0%
JS/sample_dot.js-4 63.7µs ± 0%
JS/sample_jquery.js-4 2.99ms ± 0%
JS/sample_jqueryui.js-4 5.92ms ± 2%
JS/sample_moment.js-4 1.09ms ± 1%
JSON/sample_large.json-4 2.95ms ± 0%
JSON/sample_testsuite.json-4 1.51ms ± 1%
JSON/sample_twitter.json-4 6.75µs ± 1%
SVG/sample_arctic.svg-4 62.3ms ± 1%
SVG/sample_gopher.svg-4 218µs ± 0%
SVG/sample_usa.svg-4 33.1ms ± 3%
XML/sample_books.xml-4 36.2µs ± 0%
XML/sample_catalog.xml-4 14.9µs ± 0%
XML/sample_omg.xml-4 6.31ms ± 1%
name speed
CSS/sample_bootstrap.css-4 60.8MB/s ± 0%
CSS/sample_gumby.css-4 63.9MB/s ± 1%
HTML/sample_amazon.html-4 203MB/s ± 2%
HTML/sample_bbc.html-4 113MB/s ± 1%
HTML/sample_blogpost.html-4 123MB/s ± 2%
HTML/sample_es6.html-4 70.7MB/s ± 0%
HTML/sample_stackoverflow.html-4 85.2MB/s ± 1%
HTML/sample_wikipedia.html-4 93.6MB/s ± 0%
JS/sample_ace.js-4 86.9MB/s ± 0%
JS/sample_dot.js-4 81.0MB/s ± 0%
JS/sample_jquery.js-4 82.8MB/s ± 0%
JS/sample_jqueryui.js-4 79.3MB/s ± 2%
JS/sample_moment.js-4 91.2MB/s ± 1%
JSON/sample_large.json-4 258MB/s ± 0%
JSON/sample_testsuite.json-4 457MB/s ± 1%
JSON/sample_twitter.json-4 226MB/s ± 1%
SVG/sample_arctic.svg-4 23.6MB/s ± 1%
SVG/sample_gopher.svg-4 26.7MB/s ± 0%
SVG/sample_usa.svg-4 30.9MB/s ± 3%
XML/sample_books.xml-4 122MB/s ± 0%
XML/sample_catalog.xml-4 130MB/s ± 0%
XML/sample_omg.xml-4 180MB/s ± 1%
HTML (with JS and CSS) minification typically shaves off about 10%.
The HTML5 minifier uses these minifications:
html, head, body, ...)tr, td, li, ... and often p)http:, https: and javascript:)doctype and meta charsetOptions:
KeepConditionalComments preserve all IE conditional comments such as <!--[if IE 6]><![endif]--> and <![if IE 6]><![endif]>, see https://msdn.microsoft.com/en-us/library/ms537512(v=vs.85).aspx#syntaxKeepDefaultAttrVals preserve default attribute values such as <script type="text/javascript">KeepDocumentTags preserve html, head and body tagsKeepEndTags preserve all end tagsKeepWhitespace preserve whitespace between inline tags but still collapse multiple whitespace characters into oneAfter 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. If the sequence contained a newline or carriage return it will collapse into a newline character instead. 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 shaves off about 10%-15%.
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.
Options:
Decimals number of decimals to preserve for numbers, -1 means no trimmingThe 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.
Common speeds of PHP and JS implementations are about 100-300kB/s (see Uglify2, Adventures in PHP web asset minimization). This implementation or orders of magnitude faster, around ~80MB/s.
TODO:
Minification typically 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, metadatapx unitpath datarect, line, polygon, polyline to pathTODO:
Options:
Decimals number of decimals to preserve for numbers, -1 means no trimmingThe XML minifier uses these minifications:
Options:
KeepWhitespace preserve whitespace between inline tags but still collapse multiple whitespace characters into oneAny input stream is being buffered by the minification functions. This is how the underlying buffer package inherently works to ensure high performance. The output stream however is not buffered. It is wise to preallocate a buffer as big as the input to which the output is written, or otherwise use bufio to buffer to a streaming writer.
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)
You can set options to several minifiers.
m.Add("text/html", &html.Minifier{
KeepDefaultAttrVals: true,
KeepWhitespace: true,
})
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 from and to a []byte for a specific mediatype.
b, err = m.Bytes(mediatype, b)
if err != nil {
panic(err)
}
Minify from and to a string for a specific mediatype.
s, err = m.String(mediatype, s)
if err != nil {
panic(err)
}
Get a minifying reader for a specific mediatype.
mr := m.Reader(mediatype, r)
if _, err := mr.Read(b); err != nil {
panic(err)
}
Get a minifying writer for a specific mediatype. Must be explicitly closed because it uses an io.Pipe underneath.
mw := m.Writer(mediatype, w)
if mw.Write([]byte("input")); err != nil {
panic(err)
}
if err := mw.Close(); err != nil {
panic(err)
}
Minify resources on the fly using middleware. It passes a wrapped response writer to the handler that removes the Content-Length header. The minifier is chosen based on the Content-Type header or, if the header is empty, by the request URI file extension. This is on-the-fly processing, you should preferably cache the results though!
fs := http.FileServer(http.Dir("www/"))
http.Handle("/", m.Middleware(fs))
Add a minifier for a specific mimetype.
type CustomMinifier struct {
KeepLineBreaks bool
}
func (c *CustomMinifier) Minify(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {
// ...
return nil
}
m.Add(mimetype, &CustomMinifier{KeepLineBreaks: true})
// or
m.AddRegexp(regexp.MustCompile("/x-custom$"), &CustomMinifier{KeepLineBreaks: true})
Add a minify function for a specific mimetype.
m.AddFunc(mimetype, func(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {
// ...
return nil
})
m.AddFuncRegexp(regexp.MustCompile("/x-custom$"), func(m *minify.M, w io.Writer, r io.Reader, params map[string]string) error {
// ...
return nil
})
Add a command cmd with arguments args for a specific mimetype.
m.AddCmd(mimetype, exec.Command(cmd, args...))
m.AddCmdRegexp(regexp.MustCompile("/x-custom$"), exec.Command(cmd, args...))
Using the params map[string]string argument one can pass parameters to the minifier such as seen in mediatypes (type/subtype; key1=val2; key2=val2). Examples are the encoding or charset of the data. Calling Minify will split the mimetype and parameters for the minifiers for you, but MinifyMimetype can be used if you already have them split up.
Minifiers can also be added using a regular expression. For example a minifier with image/.* will match any image mime.
Basic example that minifies from stdin to stdout and loads the default HTML, CSS and JS minifiers. Optionally, one can enable java -jar build/compiler.jar to run for JS (for example the ClosureCompiler). Note that reading the file into a buffer first and writing to a pre-allocated buffer would be faster (but would disable streaming).
package main
import (
"log"
"os"
"os/exec"
"github.com/tdewolff/minify"
"github.com/tdewolff/minify/css"
"github.com/tdewolff/minify/html"
"github.com/tdewolff/minify/js"
"github.com/tdewolff/minify/json"
"github.com/tdewolff/minify/svg"
"github.com/tdewolff/minify/xml"
)
func main() {
m := minify.New()
m.AddFunc("text/css", css.Minify)
m.AddFunc("text/html", html.Minify)
m.AddFunc("text/javascript", js.Minify)
m.AddFunc("image/svg+xml", svg.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]json$"), json.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]xml$"), xml.Minify)
// Or use the following for better minification of JS but lower speed:
// m.AddCmd("text/javascript", exec.Command("java", "-jar", "build/compiler.jar"))
if err := m.Minify("text/html", os.Stdout, os.Stdin); err != nil {
panic(err)
}
}
Custom minifier showing an example that implements the minifier function interface. Within a custom minifier, it is possible to call any minifier function (through m minify.Minifier) recursively when dealing with embedded resources.
package main
import (
"bufio"
"fmt"
"io"
"log"
"strings"
"github.com/tdewolff/minify"
)
func main() {
m := minify.New()
m.AddFunc("text/plain", func(m *minify.M, w io.Writer, r io.Reader, _ map[string]string) error {
// remove newlines and spaces
rb := bufio.NewReader(r)
for {
line, err := rb.ReadString('\n')
if err != nil && err != io.EOF {
return err
}
if _, errws := io.WriteString(w, strings.Replace(line, " ", "", -1)); errws != nil {
return errws
}
if err == io.EOF {
break
}
}
return nil
})
in := "Because my coffee was too cold, I heated it in the microwave."
out, err := m.String("text/plain", in)
if err != nil {
panic(err)
}
fmt.Println(out)
// Output: Becausemycoffeewastoocold,Iheateditinthemicrowave.
}
func main() {
m := minify.New()
m.AddFunc("text/css", css.Minify)
m.AddFunc("text/html", html.Minify)
m.AddFunc("text/javascript", js.Minify)
m.AddFunc("image/svg+xml", svg.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]json$"), json.Minify)
m.AddFuncRegexp(regexp.MustCompile("[/+]xml$"), xml.Minify)
fs := http.FileServer(http.Dir("www/"))
http.Handle("/", m.Middleware(fs))
}
func Serve(w http.ResponseWriter, r *http.Request) {
mw := m.ResponseWriter(w, r)
defer mw.Close()
w = mw
http.ServeFile(w, r, path.Join("www", r.URL.Path))
}
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.WriteCloser
}
func (m MinifyResponseWriter) Write(b []byte) (int, error) {
return m.WriteCloser.Write(b)
}
// MinifyResponseWriter must be closed explicitly by calling site.
func MinifyFilter(mediatype string, res http.ResponseWriter) MinifyResponseWriter {
m := minify.New()
// add minfiers
mw := m.Writer(mediatype, res)
return MinifyResponseWriter{res, mw}
}
// Usage
func(w http.ResponseWriter, req *http.Request) {
w = MinifyFilter("text/html", w)
if _, err := io.WriteString(w, "<p class="message"> This HTTP response will be minified. </p>"); err != nil {
panic(err)
}
if err := w.Close(); err != nil {
panic(err)
}
// Output: <p class=message>This HTTP response will be minified.
}
Here's an example of a replacement for template.ParseFiles from template/html, which automatically minifies each template before parsing it.
Be aware that minifying templates will work in most cases but not all. Because the HTML minifier only works for valid HTML5, your template must be valid HTML5 of itself. Template tags are parsed as regular text by the minifier.
func compileTemplates(filenames ...string) (*template.Template, error) {
m := minify.New()
m.AddFunc("text/html", html.Minify)
var tmpl *template.Template
for _, filename := range filenames {
name := filepath.Base(filename)
if tmpl == nil {
tmpl = template.New(name)
} else {
tmpl = tmpl.New(name)
}
b, err := ioutil.ReadFile(filename)
if err != nil {
return nil, err
}
mb, err := m.Bytes("text/html", b)
if err != nil {
return nil, err
}
tmpl.Parse(string(mb))
}
return tmpl, nil
}
Example usage:
templates := template.MustCompile(compileTemplates("view.html", "home.html"))
Released under the MIT license.
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