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Javascript-based HTML compressor/minifier (with Node.js support)
HTML JavaScript

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README.md

NPM version Build Status Dependency Status devDependency Status

HTMLMinifier is a highly configurable, well-tested, Javascript-based HTML minifier, with lint-like capabilities.

See corresponding blog post for all the gory details of how it works, description of each option, testing results and conclusions.

Test suite is available online.

Also see corresponding Ruby wrapper, and for Node.js, Grunt plugin, Gulp module, and Koa middleware wrapper.

How does HTMLMinifier compare to another solution — HTML Minifier from Will Peavy (1st result in google search for "html minifier") as well as htmlcompressor.com?

Site Original size (KB) HTMLMinifier (KB) Will Peavy (KB) htmlcompressor.com (KB)
HTMLMinifier page 48.8 37.3 43.3 41.9
ES6 table 117.9 79.9 92 91.9
MSN 156.6 133 145 138.3
Stackoverflow 200.4 159.5 168.3 163.3
Amazon 245.9 206.3 225 218.5
Wikipedia 401.4 380.6 396.3 n/a
Eloquent Javascript 869.5 830 872 n/a

Options Quick Reference

Option Description Default
removeComments Strip HTML comments false
removeCommentsFromCDATA Strip HTML comments from scripts and styles false
removeCDATASectionsFromCDATA Remove CDATA sections from script and style elements false
collapseWhitespace Collapse white space that contributes to text nodes in a document tree. false
conservativeCollapse Always collapse to 1 space (never remove it entirely). Must be used in conjunction with collapseWhitespace=true false
preserveLineBreaks Always collapse to 1 line break (never remove it entirely) when whitespace between tags include a line break. Must be used in conjunction with collapseWhitespace=true false
collapseBooleanAttributes Omit attribute values from boolean attributes false
removeAttributeQuotes Remove quotes around attributes when possible. false
removeRedundantAttributes Remove attributes when value matches default. false
preventAttributesEscaping Prevents the escaping of the values of attributes. false
useShortDoctype Replaces the doctype with the short (HTML5) doctype false
removeEmptyAttributes Remove all attributes with whitespace-only values false
removeScriptTypeAttributes Remove type="text/javascript" from script tags. Other type attribute values are left intact. false
removeStyleLinkTypeAttributes Remove type="text/css" from style and link tags. Other type attribute values are left intact. false
removeOptionalTags Remove unrequired tags false
removeIgnored Remove all tags starting and ending with <%, %>, <?, ?> false
removeEmptyElements Remove all elements with empty contents false
lint Toggle linting false
keepClosingSlash Keep the trailing slash on singleton elements false
caseSensitive Treat attributes in case sensitive manner (useful for custom HTML tags.) false
minifyJS Minify Javascript in script elements and on* attributes (uses UglifyJS) false (could be true, false, Object (options))
minifyCSS Minify CSS in style elements and style attributes (uses clean-css) false (could be true, false, Object (options))
minifyURLs Minify URLs in various attributes (uses relateurl) false (could be Object (options))
ignoreCustomComments Array of regex'es that allow to ignore certain comments, when matched [ ]
processScripts Array of strings corresponding to types of script elements to process through minifier (e.g. text/ng-template, text/x-handlebars-template, etc.) [ ]
maxLineLength Specify a maximum line length. Compressed output will be split by newlines at valid HTML split-points.
customAttrAssign Arrays of regex'es that allow to support custom attribute assign expressions (e.g. '<div flex?="{{mode != cover}}"></div>') [ ]
customAttrSurround Arrays of regex'es that allow to support custom attribute surround expressions (e.g. <input {{#if value}}checked="checked"{{/if}}>) [ ]
customAttrCollapse Regex that specifies custom attribute to strip newlines from (e.g. /ng\-class/)

Special cases

Ignoring chunks of markup.

If you have chunks of markup you would like preserved, you can wrap them <!-- htmlmin:ignore -->.

Preserving SVG tags

SVG tags are automatically recognized, and when they are minified, both case-sensitivity and closing-slashes are preserved, regardless of the minification settings used for the rest of the file.

Working with invalid markup

HTMLMinifier can't work with invalid or partial chunks of markup. This is because it parses markup into a tree struture, then modifies it (removing anything that was specified for removal, ignoring anything that was specified to be ingored, etc.), then it creates a markup out of that tree and returns it.

Input markup (e.g. <p id="">foo)

Internal representation of markup in a form of tree (e.g. {tag: "p", attr: "id", children: ["foo"] })

Transformation of internal representation (e.g. removal of "id" attribute)

Output of resulting markup (e.g. <p>foo</p>)

HTMLMinifier can't know that original markup was only half of the tree; it does its best to try to parse it as a full tree and it loses information about tree being malformed or partial in the beginning. As a result, it can't create a partial/malformed tree at the time of the output.

Installation Instructions

From NPM for use as a command line app:

npm install html-minifier -g

From NPM for programmatic use:

npm install html-minifier

From Git:

git clone git://github.com/kangax/html-minifier.git
cd html-minifier
npm link .

Usage

For command line usage please see html-minifier --help

Node.js

var minify = require('html-minifier').minify;
var result = minify('<p title="blah" id="moo">foo</p>', {
  removeAttributeQuotes: true
});
result; // '<p title=blah id=moo>foo</p>'

Running benchmarks

Benchmarks for minified HTML:

node benchmark.js
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