Minify

Go minifiers for web formats

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Install / Use

/learn @tdewolff/Minify

About this skill

Quality Score

0/100

README

Minify <a name="minify"></a>

Online demo if you need to minify files now.

Binaries of CLI for various platforms. See CLI for more installation instructions.

Windows binary from scoop install with scoop install main/minify

Python bindings install with pip install tdewolff-minify

JavaScript bindings install with npm i @tdewolff/minify

.NET bindings install with Install-Package NMinify or dotnet add package NMinify, thanks to Jonas Kamsker for the port

Did you know that the shortest valid piece of HTML5 is <!doctype html><title>x</title>? See for yourself at the W3C Validator!

Minify is a minifier package written in [Go][1]. 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 (see https://github.com/privatenumber/minification-benchmarks where this library is (one of) the fastest JS minifiers).

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, ...).

Roadmap

[ ] Use ASM/SSE to further speed-up core parts of the parsers/minifiers
[x] Improve JS minifiers by shortening variables and proper semicolon omission
[ ] Speed-up SVG minifier, it is very slow
[x] Proper parser error reporting and line number + column information
[ ] Generation of source maps (uncertain, might slow down parsers too much if it cannot run separately nicely)
[ ] Create a cmd to pack webfiles (much like webpack), ie. merging CSS and JS files, inlining small external files, minification and gzipping. This would work on HTML files.

Prologue

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.

Installation

Make sure you have Git and Go (1.18 or higher) installed, run

mkdir Project
cd Project
go mod init
go get -u github.com/tdewolff/minify/v2

Then add the following imports to be able to use the various minifiers

import (
	"github.com/tdewolff/minify/v2"
	"github.com/tdewolff/minify/v2/css"
	"github.com/tdewolff/minify/v2/html"
	"github.com/tdewolff/minify/v2/js"
	"github.com/tdewolff/minify/v2/json"
	"github.com/tdewolff/minify/v2/svg"
	"github.com/tdewolff/minify/v2/xml"
)

You can optionally run go mod tidy to clean up the go.mod and go.sum files.

See CLI tool for installation instructions of the binary.

Docker

If you want to use Docker, please see https://hub.docker.com/r/tdewolff/minify.

$ docker run -it tdewolff/minify --help

API stability

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.

Testing

For all subpackages and the imported parse package, 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. These tests ensure that everything works as intended and that the code does not crash (whatever the input). If you still encounter a bug, please file a bug report!

Performance

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 1.15.

name                              time/op
CSS/sample_bootstrap.css-4          2.70ms ± 0%
CSS/sample_gumby.css-4              3.57ms ± 0%
CSS/sample_fontawesome.css-4         767µs ± 0%
CSS/sample_normalize.css-4          85.5µs ± 0%
HTML/sample_amazon.html-4           15.2ms ± 0%
HTML/sample_bbc.html-4              3.90ms ± 0%
HTML/sample_blogpost.html-4          420µs ± 0%
HTML/sample_es6.html-4              15.6ms ± 0%
HTML/sample_stackoverflow.html-4    3.73ms ± 0%
HTML/sample_wikipedia.html-4        6.60ms ± 0%
JS/sample_ace.js-4                  28.7ms ± 0%
JS/sample_dot.js-4                   357µs ± 0%
JS/sample_jquery.js-4               10.0ms ± 0%
JS/sample_jqueryui.js-4             20.4ms ± 0%
JS/sample_moment.js-4               3.47ms ± 0%
JSON/sample_large.json-4            3.25ms ± 0%
JSON/sample_testsuite.json-4        1.74ms ± 0%
JSON/sample_twitter.json-4          24.2µs ± 0%
SVG/sample_arctic.svg-4             34.7ms ± 0%
SVG/sample_gopher.svg-4              307µs ± 0%
SVG/sample_usa.svg-4                57.4ms ± 0%
SVG/sample_car.svg-4                18.0ms ± 0%
SVG/sample_tiger.svg-4              5.61ms ± 0%
XML/sample_books.xml-4              54.7µs ± 0%
XML/sample_catalog.xml-4            33.0µs ± 0%
XML/sample_omg.xml-4                7.17ms ± 0%

name                              speed
CSS/sample_bootstrap.css-4        50.7MB/s ± 0%
CSS/sample_gumby.css-4            52.1MB/s ± 0%
CSS/sample_fontawesome.css-4      61.2MB/s ± 0%
CSS/sample_normalize.css-4        70.8MB/s ± 0%
HTML/sample_amazon.html-4         31.1MB/s ± 0%
HTML/sample_bbc.html-4            29.5MB/s ± 0%
HTML/sample_blogpost.html-4       49.8MB/s ± 0%
HTML/sample_es6.html-4            65.6MB/s ± 0%
HTML/sample_stackoverflow.html-4  55.0MB/s ± 0%
HTML/sample_wikipedia.html-4      67.5MB/s ± 0%
JS/sample_ace.js-4                22.4MB/s ± 0%
JS/sample_dot.js-4                14.5MB/s ± 0%
JS/sample_jquery.js-4             24.8MB/s ± 0%
JS/sample_jqueryui.js-4           23.0MB/s ± 0%
JS/sample_moment.js-4             28.6MB/s ± 0%
JSON/sample_large.json-4           234MB/s ± 0%
JSON/sample_testsuite.json-4       394MB/s ± 0%
JSON/sample_twitter.json-4        63.0

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Audited on Mar 23, 2026

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