Highlight.js
JavaScript syntax highlighter with language auto-detection and zero dependencies.
Install / Use
/learn @highlightjs/Highlight.jsREADME
Highlight.js
Highlight.js is a syntax highlighter written in JavaScript. It works in the browser as well as on the server. It can work with pretty much any markup, doesn’t depend on any other frameworks, and has automatic language detection.
Contents
- Basic Usage
- Supported Languages
- Custom Usage
- Importing the Library
- Getting the Library
- Requirements
- License
- Links
Upgrading to Version 11
As always, major releases do contain breaking changes which may require action from users. Please read VERSION_11_UPGRADE.md for a detailed summary of breaking changes and any actions you may need to take.
Support for older versions <!-- omit in toc -->
Please see SECURITY.md for long-term support information.
Basic Usage
In the Browser
The bare minimum for using highlight.js on a web page is linking to the
library along with one of the themes and calling [highlightAll][1]:
<link rel="stylesheet" href="/path/to/styles/default.min.css">
<script src="/path/to/highlight.min.js"></script>
<script>hljs.highlightAll();</script>
This will find and highlight code inside of <pre><code> tags; it tries
to detect the language automatically. If automatic detection doesn’t
work for you, or you simply prefer to be explicit, you can specify the language manually by using the class attribute:
<pre><code class="language-html">...</code></pre>
Plaintext Code Blocks
To apply the Highlight.js styling to plaintext without actually highlighting it, use the plaintext language:
<pre><code class="language-plaintext">...</code></pre>
Ignoring a Code Block
To skip highlighting of a code block completely, use the nohighlight class:
<pre><code class="nohighlight">...</code></pre>
Node.js on the Server
The bare minimum to auto-detect the language and highlight some code.
// load the library and ALL languages
hljs = require('highlight.js');
html = hljs.highlightAuto('<h1>Hello World!</h1>').value
To load only a "common" subset of popular languages:
hljs = require('highlight.js/lib/common');
To highlight code with a specific language, use highlight:
html = hljs.highlight('<h1>Hello World!</h1>', {language: 'xml'}).value
See Importing the Library for more examples of require vs import usage, etc. For more information about the result object returned by highlight or highlightAuto refer to the api docs.
Supported Languages
Highlight.js supports over 180 languages in the core library. There are also 3rd party language definitions available to support even more languages. You can find the full list of supported languages in [SUPPORTED_LANGUAGES.md][9].
Custom Usage
If you need a bit more control over the initialization of
Highlight.js, you can use the [highlightElement][3] and [configure][4]
functions. This allows you to better control what to highlight and when.
For example, here’s the rough equivalent of calling [highlightAll][1] but doing the work manually instead:
document.addEventListener('DOMContentLoaded', (event) => {
document.querySelectorAll('pre code').forEach((el) => {
hljs.highlightElement(el);
});
});
Please refer to the documentation for [configure][4] options.
Using custom HTML
We strongly recommend <pre><code> wrapping for code blocks. It's quite
semantic and "just works" out of the box with zero fiddling. It is possible to
use other HTML elements (or combos), but you may need to pay special attention to
preserving linebreaks.
Let's say your markup for code blocks uses divs:
<div class='code'>...</div>
To highlight such blocks manually:
// first, find all the div.code blocks
document.querySelectorAll('div.code').forEach(el => {
// then highlight each
hljs.highlightElement(el);
});
Without using a tag that preserves linebreaks (like pre) you'll need some
additional CSS to help preserve them. You could also pre and post-process line
breaks with a plug-in, but we recommend using CSS.
To preserve linebreaks inside a div using CSS:
div.code {
white-space: pre;
}
Using with Vue.js
See highlightjs/vue-plugin for a simple Vue plugin that works great with Highlight.js.
An example of vue-plugin in action:
<div id="app">
<!-- bind to a data property named `code` -->
<highlightjs autodetect :code="code" />
<!-- or literal code works as well -->
<highlightjs language='javascript' code="var x = 5;" />
</div>
Using Web Workers
You can run highlighting inside a web worker to avoid freezing the browser window while dealing with very big chunks of code.
In your main script:
addEventListener('load', () => {
const code = document.querySelector('#code');
const worker = new Worker('worker.js');
worker.onmessage = (event) => { code.innerHTML = event.data; }
worker.postMessage(code.textContent);
});
In worker.js:
onmessage = (event) => {
importScripts('<path>/highlight.min.js');
const result = self.hljs.highlightAuto(event.data);
postMessage(result.value);
};
Importing the Library
First, you'll likely be installing the library via npm or yarn -- see Getting the Library.
Node.js CommonJS Modules / require
Requiring the top-level library will load all languages:
// require the highlight.js library, including all languages
const hljs = require('./highlight.js');
const highlightedCode = hljs.highlightAuto('<span>Hello World!</span>').value
For a smaller footprint, load our common subset of languages (the same set used for our default web build).
const hljs = require('highlight.js/lib/common');
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