167 lines
13 KiB
Markdown
167 lines
13 KiB
Markdown
# HTMLMinifier
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[](https://www.npmjs.com/package/html-minifier-terser)
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[](https://github.com/terser/html-minifier-terser/actions?workflow=CI)
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[HTMLMinifier](https://terser.org/html-minifier-terser/) is a highly **configurable**, **well-tested**, JavaScript-based HTML minifier.
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See [corresponding blog post](http://perfectionkills.com/experimenting-with-html-minifier/) for all the gory details of [how it works](http://perfectionkills.com/experimenting-with-html-minifier/#how_it_works), [description of each option](http://perfectionkills.com/experimenting-with-html-minifier/#options), [testing results](http://perfectionkills.com/experimenting-with-html-minifier/#field_testing) and [conclusions](http://perfectionkills.com/experimenting-with-html-minifier/#cost_and_benefits).
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[Test suite is available online](https://terser.org/html-minifier-terser/tests/).
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Also see corresponding [Ruby wrapper](https://github.com/stereobooster/html_minifier), and for Node.js, [Grunt plugin](https://github.com/gruntjs/grunt-contrib-htmlmin), [Gulp module](https://github.com/jonschlinkert/gulp-htmlmin), [Koa middleware wrapper](https://github.com/koajs/html-minifier) and [Express middleware wrapper](https://github.com/melonmanchan/express-minify-html).
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For lint-like capabilities take a look at [HTMLLint](https://github.com/kangax/html-lint).
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## Minification comparison
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How does HTMLMinifier compare to other solutions — [HTML Minifier from Will Peavy](http://www.willpeavy.com/minifier/) (1st result in [Google search for "html minifier"](https://www.google.com/#q=html+minifier)) as well as [htmlcompressor.com](http://htmlcompressor.com) and [minimize](https://github.com/Swaagie/minimize)?
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| Site | Original size *(KB)* | HTMLMinifier | minimize | Will Peavy | htmlcompressor.com |
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| ---------------------------------------------------------------------------- |:--------------------:| ------------:| --------:| ----------:| ------------------:|
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| [Google](https://www.google.com/) | 45 | **41** | 45 | 46 | 45 |
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| [Stack Overflow](https://stackoverflow.com/) | 115 | **82** | 90 | 92 | 88 |
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| [HTMLMinifier](https://github.com/kangax/html-minifier) | 132 | **105** | 118 | 123 | 118 |
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| [Bootstrap CSS](https://getbootstrap.com/docs/3.3/css/) | 271 | **260** | 269 | 229 | 269 |
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| [Twitter](https://twitter.com/) | 289 | **238** | 282 | 314 | 282 |
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| [BBC](https://www.bbc.co.uk/) | 298 | **233** | 289 | 291 | 269 |
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| [Wikipedia](https://en.wikipedia.org/wiki/President_of_the_United_States) | 574 | **468** | 557 | 578 | 557 |
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| [Amazon](https://www.amazon.co.uk/) | 702 | **343** | 692 | 704 | n/a |
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| [NBC](https://www.nbc.com/) | 844 | **805** | 843 | 844 | n/a |
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| [Eloquent Javascript](https://eloquentjavascript.net/1st_edition/print.html) | 870 | **815** | 840 | 864 | n/a |
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| [New York Times](https://www.nytimes.com/) | 1304 | **1183** | 1301 | 1295 | n/a |
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| [ES draft](https://tc39.github.io/ecma262/) | 6347 | **5686** | 5863 | n/a | n/a |
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## Options Quick Reference
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Most of the options are disabled by default.
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| Option | Description | Default |
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|--------------------------------|-----------------|---------|
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| `caseSensitive` | Treat attributes in case sensitive manner (useful for custom HTML tags) | `false` |
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| `collapseBooleanAttributes` | [Omit attribute values from boolean attributes](http://perfectionkills.com/experimenting-with-html-minifier/#collapse_boolean_attributes) | `false` |
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| `collapseInlineTagWhitespace` | Don't leave any spaces between `display:inline;` elements when collapsing. Must be used in conjunction with `collapseWhitespace=true` | `false` |
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| `collapseWhitespace` | [Collapse white space that contributes to text nodes in a document tree](http://perfectionkills.com/experimenting-with-html-minifier/#collapse_whitespace) | `false` |
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| `conservativeCollapse` | Always collapse to 1 space (never remove it entirely). Must be used in conjunction with `collapseWhitespace=true` | `false` |
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| `continueOnParseError` | [Handle parse errors](https://html.spec.whatwg.org/multipage/parsing.html#parse-errors) instead of aborting. | `false` |
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| `customAttrAssign` | Arrays of regex'es that allow to support custom attribute assign expressions (e.g. `'<div flex?="{{mode != cover}}"></div>'`) | `[ ]` |
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| `customAttrCollapse` | Regex that specifies custom attribute to strip newlines from (e.g. `/ng-class/`) | |
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| `customAttrSurround` | Arrays of regex'es that allow to support custom attribute surround expressions (e.g. `<input {{#if value}}checked="checked"{{/if}}>`) | `[ ]` |
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| `customEventAttributes` | Arrays of regex'es that allow to support custom event attributes for `minifyJS` (e.g. `ng-click`) | `[ /^on[a-z]{3,}$/ ]` |
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| `decodeEntities` | Use direct Unicode characters whenever possible | `false` |
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| `html5` | Parse input according to HTML5 specifications | `true` |
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| `ignoreCustomComments` | Array of regex'es that allow to ignore certain comments, when matched | `[ /^!/, /^\s*#/ ]` |
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| `ignoreCustomFragments` | Array of regex'es that allow to ignore certain fragments, when matched (e.g. `<?php ... ?>`, `{{ ... }}`, etc.) | `[ /<%[\s\S]*?%>/, /<\?[\s\S]*?\?>/ ]` |
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| `includeAutoGeneratedTags` | Insert tags generated by HTML parser | `true` |
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| `keepClosingSlash` | Keep the trailing slash on singleton elements | `false` |
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| `maxLineLength` | Specify a maximum line length. Compressed output will be split by newlines at valid HTML split-points |
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| `minifyCSS` | Minify CSS in style elements and style attributes (uses [clean-css](https://github.com/jakubpawlowicz/clean-css)) | `false` (could be `true`, `Object`, `Function(text, type)`) |
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| `minifyJS` | Minify JavaScript in script elements and event attributes (uses [Terser](https://github.com/terser/terser)) | `false` (could be `true`, `Object`, `Function(text, inline)`) |
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| `minifyURLs` | Minify URLs in various attributes (uses [relateurl](https://github.com/stevenvachon/relateurl)) | `false` (could be `String`, `Object`, `Function(text)`) |
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| `noNewlinesBeforeTagClose` | Never add a newline before a tag that closes an element | `false` |
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| `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` |
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| `preventAttributesEscaping` | Prevents the escaping of the values of attributes | `false` |
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| `processConditionalComments` | Process contents of conditional comments through minifier | `false` |
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| `processScripts` | Array of strings corresponding to types of script elements to process through minifier (e.g. `text/ng-template`, `text/x-handlebars-template`, etc.) | `[ ]` |
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| `quoteCharacter` | Type of quote to use for attribute values (' or ") | |
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| `removeAttributeQuotes` | [Remove quotes around attributes when possible](http://perfectionkills.com/experimenting-with-html-minifier/#remove_attribute_quotes) | `false` |
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| `removeComments` | [Strip HTML comments](http://perfectionkills.com/experimenting-with-html-minifier/#remove_comments) | `false` |
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| `removeEmptyAttributes` | [Remove all attributes with whitespace-only values](http://perfectionkills.com/experimenting-with-html-minifier/#remove_empty_or_blank_attributes) | `false` (could be `true`, `Function(attrName, tag)`) |
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| `removeEmptyElements` | [Remove all elements with empty contents](http://perfectionkills.com/experimenting-with-html-minifier/#remove_empty_elements) | `false` |
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| `removeOptionalTags` | [Remove optional tags](http://perfectionkills.com/experimenting-with-html-minifier/#remove_optional_tags) | `false` |
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| `removeRedundantAttributes` | [Remove attributes when value matches default.](http://perfectionkills.com/experimenting-with-html-minifier/#remove_redundant_attributes) | `false` |
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| `removeScriptTypeAttributes` | Remove `type="text/javascript"` from `script` tags. Other `type` attribute values are left intact | `false` |
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| `removeStyleLinkTypeAttributes`| Remove `type="text/css"` from `style` and `link` tags. Other `type` attribute values are left intact | `false` |
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| `removeTagWhitespace` | Remove space between attributes whenever possible. **Note that this will result in invalid HTML!** | `false` |
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| `sortAttributes` | [Sort attributes by frequency](#sorting-attributes--style-classes) | `false` |
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| `sortClassName` | [Sort style classes by frequency](#sorting-attributes--style-classes) | `false` |
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| `trimCustomFragments` | Trim white space around `ignoreCustomFragments`. | `false` |
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| `useShortDoctype` | [Replaces the `doctype` with the short (HTML5) doctype](http://perfectionkills.com/experimenting-with-html-minifier/#use_short_doctype) | `false` |
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### Sorting attributes / style classes
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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.
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## Special cases
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### Ignoring chunks of markup
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If you have chunks of markup you would like preserved, you can wrap them `<!-- htmlmin:ignore -->`.
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### Preserving SVG tags
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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.
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### Working with invalid markup
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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.
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Input markup (e.g. `<p id="">foo`)
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↓
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Internal representation of markup in a form of tree (e.g. `{ tag: "p", attr: "id", children: ["foo"] }`)
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↓
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Transformation of internal representation (e.g. removal of `id` attribute)
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↓
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Output of resulting markup (e.g. `<p>foo</p>`)
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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.
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## Installation Instructions
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From NPM for use as a command line app:
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```shell
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npm install html-minifier-terser -g
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```
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From NPM for programmatic use:
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```shell
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npm install html-minifier-terser
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```
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From Git:
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```shell
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git clone git://github.com/terser/html-minifier-terser.git
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cd html-minifier-terser
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npm link .
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```
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## Usage
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Note that almost all options are disabled by default. For command line usage please see `html-minifier-terser --help` for a list of available options. Experiment and find what works best for you and your project.
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- **Sample command line:** `html-minifier-terser --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`
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### Node.js
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```js
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const { minify } = require('html-minifier-terser');
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const result = await minify('<p title="blah" id="moo">foo</p>', {
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removeAttributeQuotes: true
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});
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result; // '<p title=blah id=moo>foo</p>'
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```
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## Running benchmarks
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Benchmarks for minified HTML:
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```shell
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node benchmark.js
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```
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## Running local server
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```shell
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npm run serve
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```
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