# Highlight.js
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[](https://travis-ci.org/highlightjs/highlight.js) [](https://greenkeeper.io/)
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Highlight.js is a syntax highlighter written in JavaScript. It works in
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the browser as well as on the server. It works with pretty much any
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markup, doesn’t depend on any framework, and has automatic language
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detection.
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## Getting Started
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The bare minimum for using highlight.js on a web page is linking to the
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library along with one of the styles and calling
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[`initHighlightingOnLoad`][1]:
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```html
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<link rel="stylesheet" href="/path/to/styles/default.css">
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<script src="/path/to/highlight.pack.js"></script>
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<script>hljs.initHighlightingOnLoad();</script>
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```
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This will find and highlight code inside of `<pre><code>` tags; it tries
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to detect the language automatically. If automatic detection doesn’t
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work for you, you can specify the language in the `class` attribute:
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```html
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<pre><code class="html">...</code></pre>
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```
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The list of supported language classes is available in the [class
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reference][2]. Classes can also be prefixed with either `language-` or
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`lang-`.
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To make arbitrary text look like code, but without highlighting, use the
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`plaintext` class:
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```html
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<pre><code class="plaintext">...</code></pre>
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```
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To disable highlighting altogether use the `nohighlight` class:
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```html
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<pre><code class="nohighlight">...</code></pre>
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```
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## Custom Initialization
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When you need a bit more control over the initialization of
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highlight.js, you can use the [`highlightBlock`][3] and [`configure`][4]
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functions. This allows you to control *what* to highlight and *when*.
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Here’s an equivalent way to calling [`initHighlightingOnLoad`][1] using
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vanilla JS:
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```js
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document.addEventListener('DOMContentLoaded', (event) => {
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document.querySelectorAll('pre code').forEach((block) => {
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hljs.highlightBlock(block);
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});
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});
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```
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You can use any tags instead of `<pre><code>` to mark up your code. If
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you don't use a container that preserves line breaks you will need to
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configure highlight.js to use the `<br>` tag:
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```js
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hljs.configure({useBR: true});
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document.querySelectorAll('div.code').forEach((block) => {
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hljs.highlightBlock(block);
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});
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```
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For other options refer to the documentation for [`configure`][4].
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## Web Workers
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You can run highlighting inside a web worker to avoid freezing the browser
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window while dealing with very big chunks of code.
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In your main script:
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```js
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addEventListener('load', () => {
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const code = document.querySelector('#code');
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const worker = new Worker('worker.js');
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worker.onmessage = (event) => { code.innerHTML = event.data; }
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worker.postMessage(code.textContent);
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});
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```
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In worker.js:
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```js
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onmessage = (event) => {
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importScripts('<path>/highlight.pack.js');
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const result = self.hljs.highlightAuto(event.data);
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postMessage(result.value);
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};
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```
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## Getting the Library
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You can get highlight.js as a hosted, or custom-build, browser script or
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as a server module. Right out of the box the browser script supports
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both AMD and CommonJS, so if you wish you can use RequireJS or
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Browserify without having to build from source. The server module also
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works perfectly fine with Browserify, but there is the option to use a
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build specific to browsers rather than something meant for a server.
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Head over to the [download page][5] for all the options.
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**Don't link to GitHub directly.** The library is not supposed to work straight
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from the source, it requires building. If none of the pre-packaged options
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work for you refer to the [building documentation][6].
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**The CDN-hosted package doesn't have all the languages.** Otherwise it'd be
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too big. If you don't see the language you need in the ["Common" section][5],
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it can be added manually:
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```html
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<script
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charset="UTF-8"
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src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/9.12.0/languages/go.min.js"></script>
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```
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**On Almond.** You need to use the optimizer to give the module a name. For
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example:
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```bash
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r.js -o name=hljs paths.hljs=/path/to/highlight out=highlight.js
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```
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### CommonJS
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You can import Highlight.js as a CommonJS-module:
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```bash
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npm install highlight.js --save
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```
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In your application:
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```js
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import hljs from 'highlight.js';
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```
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The default import imports all languages! Therefore it is likely to be more efficient to import only the library and the languages you need:
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```js
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import hljs from 'highlight.js/lib/highlight';
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import javascript from 'highlight.js/lib/languages/javascript';
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hljs.registerLanguage('javascript', javascript);
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```
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To set the syntax highlighting style, if your build tool processes CSS from your JavaScript entry point, you can import the stylesheet directly into your CommonJS-module:
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```js
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import hljs from 'highlight.js/lib/highlight';
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import 'highlight.js/styles/github.css';
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```
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## License
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Highlight.js is released under the BSD License. See [LICENSE][7] file
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for details.
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## Links
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The official site for the library is at <https://highlightjs.org/>.
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Further in-depth documentation for the API and other topics is at
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<http://highlightjs.readthedocs.io/>.
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Authors and contributors are listed in the [AUTHORS.en.txt][8] file.
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[1]: http://highlightjs.readthedocs.io/en/latest/api.html#inithighlightingonload
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[2]: http://highlightjs.readthedocs.io/en/latest/css-classes-reference.html
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[3]: http://highlightjs.readthedocs.io/en/latest/api.html#highlightblock-block
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[4]: http://highlightjs.readthedocs.io/en/latest/api.html#configure-options
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[5]: https://highlightjs.org/download/
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[6]: http://highlightjs.readthedocs.io/en/latest/building-testing.html
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[7]: https://github.com/highlightjs/highlight.js/blob/master/LICENSE
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[8]: https://github.com/highlightjs/highlight.js/blob/master/AUTHORS.en.txt
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