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HTMLMinifier

HTMLMinifier is a highly configurable, well-tested, JavaScript-based HTML minifier.

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, Koa middleware wrapper and Express middleware wrapper.

For lint-like capabilities take a look at HTMLLint.

Minification comparison

How does HTMLMinifier compare to other solutions — HTML Minifier from Will Peavy (1st result in Google search for "html minifier") as well as htmlcompressor.com and minimize?

Site	Original size (KB)	HTMLMinifier	minimize	Will Peavy	htmlcompressor.com
Google	48	44	48	49	48
HTMLMinifier	154	117	128	133	128
Twitter	203	162	195	219	195
Stack Overflow	254	196	208	216	205
Bootstrap CSS	271	260	269	229	269
BBC	288	230	280	281	272
Amazon	508	439	495	501	n/a
Wikipedia	533	434	517	536	517
New York Times	699	619	693	683	n/a
NBC	700	657	698	699	n/a
Eloquent Javascript	870	815	840	864	n/a
ES6 table	5308	4529	5025	n/a	n/a
ES draft	6082	5456	5624	n/a	n/a

Options Quick Reference

Most of the options are disabled by default.

Option	Description	Default
`caseSensitive`	Treat attributes in case sensitive manner (useful for custom HTML tags)	`false`
`collapseBooleanAttributes`	Omit attribute values from boolean attributes	`false`
`collapseInlineTagWhitespace`	Don't leave any spaces between `display:inline;` elements when collapsing. Must be used in conjunction with `collapseWhitespace=true`	`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`
`customAttrAssign`	Arrays of regex'es that allow to support custom attribute assign expressions (e.g. `'<div flex?="{{mode != cover}}"></div>'`)	`[ ]`
`customAttrCollapse`	Regex that specifies custom attribute to strip newlines from (e.g. `/ng-class/`)
`customAttrSurround`	Arrays of regex'es that allow to support custom attribute surround expressions (e.g. `<input {{#if value}}checked="checked"{{/if}}>`)	`[ ]`
`customEventAttributes`	Arrays of regex'es that allow to support custom event attributes for `minifyJS` (e.g. `ng-click`)	`[ /^on[a-z]{3,}$/ ]`
`decodeEntities`	Use direct Unicode characters whenever possible	`false`
`html5`	Parse input according to HTML5 specifications	`true`
`ignoreCustomComments`	Array of regex'es that allow to ignore certain comments, when matched	`[ /^!/ ]`
`ignoreCustomFragments`	Array of regex'es that allow to ignore certain fragments, when matched (e.g. `<?php ... ?>`, `{{ ... }}`, etc.)	`[ /<%[\s\S]?%>/, /<\?[\s\S]?\?>/ ]`
`includeAutoGeneratedTags`	Insert tags generated by HTML parser	`true`
`keepClosingSlash`	Keep the trailing slash on singleton elements	`false`
`maxLineLength`	Specify a maximum line length. Compressed output will be split by newlines at valid HTML split-points
`minifyCSS`	Minify CSS in style elements and style attributes (uses clean-css)	`false` (could be `true`, `Object`, `Function(text, type)`)
`minifyJS`	Minify JavaScript in script elements and event attributes (uses UglifyJS)	`false` (could be `true`, `Object`, `Function(text, inline)`)
`minifyURLs`	Minify URLs in various attributes (uses relateurl)	`false` (could be `String`, `Object`, `Function(text)`)
`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`
`preventAttributesEscaping`	Prevents the escaping of the values of attributes	`false`
`processConditionalComments`	Process contents of conditional comments through minifier	`false`
`processScripts`	Array of strings corresponding to types of script elements to process through minifier (e.g. `text/ng-template`, `text/x-handlebars-template`, etc.)	`[ ]`
`quoteCharacter`	Type of quote to use for attribute values (' or ")
`removeAttributeQuotes`	Remove quotes around attributes when possible	`false`
`removeComments`	Strip HTML comments	`false`
`removeEmptyAttributes`	Remove all attributes with whitespace-only values	`false` (could be `true`, `Function(attrName, tag)`)
`removeEmptyElements`	Remove all elements with empty contents	`false`
`removeOptionalTags`	Remove optional tags	`false`
`removeRedundantAttributes`	Remove attributes when value matches default.	`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`
`removeTagWhitespace`	Remove space between attributes whenever possible. Note that this will result in invalid HTML!	`false`
`sortAttributes`	Sort attributes by frequency	`false`
`sortClassName`	Sort style classes by frequency	`false`
`trimCustomFragments`	Trim white space around `ignoreCustomFragments`.	`false`
`useShortDoctype`	Replaces the `doctype` with the short (HTML5) doctype	`false`

Sorting attributes / style classes

Minifier options like sortAttributes and sortClassName won't impact the plain-text size of the output. However, they form long repetitive chains of characters that should improve compression ratio of gzip used in HTTP compression.

Special cases

Ignoring chunks of markup

If you have chunks of markup you would like preserved, you can wrap them .

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 structure, then modifies it (removing anything that was specified for removal, ignoring anything that was specified to be ignored, 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

Note that almost all options are disabled by default. For command line usage please see html-minifier --help for a list of available options. Experiment and find what works best for you and your project.

Sample command line: html-minifier --collapse-whitespace --remove-comments --remove-optional-tags --remove-redundant-attributes --remove-script-type-attributes --remove-tag-whitespace --use-short-doctype --minify-css true --minify-js true

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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