HTMLMinifier is a highly configurable, well-tested, JavaScript-based HTML minifier.
From NPM for use as a command line app:
npm install html-minifier-terser -g
From NPM for programmatic use:
npm install html-minifier-terser
Note that almost all options are disabled by default. Experiment and find what works best for you and your project.
For command line usage please see html-minifier-terser --help for a list of available options.
Sample command line:
html-minifier-terser --collapse-whitespace --remove-comments --minify-js true
const { minify } = require('html-minifier-terser');
const result = await minify('<p title="blah" id="moo">foo</p>', {
removeAttributeQuotes: true,
});
result; // '<p title=blah id=moo>foo</p>'
See corresponding blog post for all the gory details of how it works, description of each option, testing results and conclusions.
Also see corresponding Ruby wrapper, and for Node.js, Grunt plugin, Gulp plugin, Koa middleware wrapper and Express middleware wrapper.
For lint-like capabilities take a look at HTMLLint.
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?
Most of the options are disabled by default.
Option Description DefaultcaseSensitive 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 continueOnParseError Handle parse errors instead of aborting. 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 [ /^!/, /^\s*#/ ] 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 Terser) false (could be true, Object, Function(text, inline)) minifyURLs Minify URLs in various attributes (uses relateurl) false (could be String, Object, Function(text)) noNewlinesBeforeTagClose Never add a newline before a tag that closes an element 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 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.
If you have chunks of markup you would like preserved, you can wrap them <!-- htmlmin:ignore -->.
You can minify script tags with JSON-LD by setting the option { processScripts: ['application/ld+json'] }. Note that this minification is very rudimentary, it is mainly useful for removing newlines and excessive whitespace.
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 markupHTMLMinifier 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.
Benchmarks for minified HTML:
cd benchmarks npm install npm run benchmark
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