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
  • In the Browser
    • Plaintext Code Blocks
    • Ignoring a Code Block
  • Node.js on the Server
• Supported Languages
• Custom Usage
  • Using custom HTML
  • Using with Vue.js
  • Using Web Workers
• Importing the Library
  • Node.js / require
  • ES6 Modules / import
• Getting the Library
  • Fetch via CDN
    • cdnjs (link)
    • jsdelivr (link)
    • unpkg (link)
    • Download prebuilt CDN assets
  • Download from our website
  • Install via NPM package
  • Build from Source
• 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

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]:

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">
    
    
    
    
  </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('</code></pre></code></pre>