highlight.js

What is highlight.js?

The highlight.js npm package is a syntax highlighter written in JavaScript. It's used to add syntax highlighting to code blocks on web pages, making them more readable and aesthetically pleasing. It supports a wide range of programming languages and is commonly used in blogs, forums, and other platforms where code is shared.

What are highlight.js's main functionalities?

Syntax Highlighting

Automatically detects and highlights syntax in code blocks on a webpage. This is the most basic usage where it applies highlighting to all code blocks.

hljs.highlightAll();

Custom Language Selection

Highlights a specific code element with a specified language. This allows for more control over which elements are highlighted and in what language.

hljs.highlightElement(document.getElementById('my-code'), {language: 'javascript', ignoreIllegals: true});

Custom Themes

Allows the use of custom themes for syntax highlighting. Themes are available as separate CSS files that can be imported to change the appearance of highlighted code.

import 'highlight.js/styles/atom-one-dark.css';

Line Numbers

Adds line numbers to code blocks. This feature is often used in conjunction with syntax highlighting to improve readability and reference specific lines of code.

document.addEventListener('DOMContentLoaded', (event) => { document.querySelectorAll('pre code').forEach((block) => { hljs.lineNumbersBlock(block); }); });

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README

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:

<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.

Custom Usage

If you need a bit more control over the initialization of Highlight.js, you can use the highlightElement and configure functions. This allows you to better control what to highlight and when.

For example, here’s the rough equivalent of calling highlightAll 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 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 / 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');

For the smallest footprint, load only the languages you need:

const hljs = require('highlight.js/lib/core');
hljs.registerLanguage('xml', require('highlight.js/lib/languages/xml'));

const highlightedCode = hljs.highlight('<span>Hello World!</span>', {language: 'xml'}).value

ES6 Modules / import

Note: You can also import directly from fully static URLs, such as our very own pre-built ES6 Module CDN resources. See Fetch via CDN for specific examples.

The default import will register all languages:

import hljs from 'highlight.js';

It is more efficient to import only the library and register the languages you need:

import hljs from 'highlight.js/lib/core';
import javascript from 'highlight.js/lib/languages/javascript';
hljs.registerLanguage('javascript', javascript);

If your build tool processes CSS imports, you can also import the theme directly as a module:

import hljs from 'highlight.js';
import 'highlight.js/styles/github.css';

Getting the Library

You can get highlight.js as a hosted, or custom-build, browser script or as a server module. Right out of the box the browser script supports both AMD and CommonJS, so if you wish you can use RequireJS or Browserify without having to build from source. The server module also works perfectly fine with Browserify, but there is the option to use a build specific to browsers rather than something meant for a server.

Do not link to GitHub directly. The library is not supposed to work straight from the source, it requires building. If none of the pre-packaged options work for you refer to the building documentation.

On Almond. You need to use the optimizer to give the module a name. For example:

r.js -o name=hljs paths.hljs=/path/to/highlight out=highlight.js

Fetch via CDN

A prebuilt version of Highlight.js bundled with many common languages is hosted by several popular CDNs. When using Highlight.js via CDN you can use Subresource Integrity for additional security. For details see DIGESTS.md.

cdnjs (link)

Common JS

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.10.0/styles/default.min.css">
<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.10.0/highlight.min.js"></script>
<!-- and it's easy to individually load additional languages -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.10.0/languages/go.min.js"></script>

ES6 Modules

<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.10.0/styles/dark.min.css">
<script type="module">
import hljs from 'https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.10.0/es/highlight.min.js';
//  and it's easy to individually load additional languages
import go from 'https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.10.0/es/languages/go.min.js';
hljs.registerLanguage('go', go);
</script>

jsdelivr (link)

Common JS

<link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@11.10.0/build/styles/default.min.css">
<script src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@11.10.0/build/highlight.min.js"></script>
<!-- and it's easy to individually load additional languages -->
<script src="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@11.10.0/build/languages/go.min.js"></script>

ES6 Modules

<link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@11.10.0/build/styles/default.min.css">
<script type="module">
import hljs from 'https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@11.10.0/build/es/highlight.min.js';
//  and it's easy to individually load additional languages
import go from 'https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@11.10.0/build/es/languages/go.min.js';
hljs.registerLanguage('go', go);
</script>

unpkg (link)

Common JS

<link rel="stylesheet" href="https://unpkg.com/@highlightjs/cdn-assets@11.10.0/styles/default.min.css">
<script src="https://unpkg.com/@highlightjs/cdn-assets@11.10.0/highlight.min.js"></script>
<!-- and it's easy to individually load additional languages -->
<script src="https://unpkg.com/@highlightjs/cdn-assets@11.10.0/languages/go.min.js"></script>

ES6 Modules

<link rel="stylesheet" href="https://unpkg.com/@highlightjs/cdn-assets@11.10.0/styles/default.min.css">
<script type="module">
import hljs from 'https://unpkg.com/@highlightjs/cdn-assets@11.10.0/es/highlight.min.js';
//  and it's easy to individually load & register additional languages
import go from 'https://unpkg.com/@highlightjs/cdn-assets@11.10.0/es/languages/go.min.js';
hljs.registerLanguage('go', go);
</script>

Note: The CDN-hosted highlight.min.js package doesn't bundle every language. It would be very large. You can find our list of "common" languages that we bundle by default on our download page.

Download prebuilt CDN assets

You can also download and self-host the same assets we serve up via our own CDNs. We publish those builds to the cdn-release GitHub repository. You can easily pull individual files off the CDN endpoints with curl, etc; if say you only needed highlight.min.js and a single CSS file.

There is also an npm package @highlightjs/cdn-assets if pulling the assets in via npm or yarn would be easier for your build process.

Download from our website

The download page can quickly generate a custom single-file minified bundle including only the languages you desire.

Note: Building from source can produce slightly smaller builds than the website download.

Install via NPM package

Our NPM package including all supported languages can be installed with NPM or Yarn:

npm install highlight.js
# or
yarn add highlight.js

Alternatively, you can build the NPM package from source.

Build from Source

The current source code is always available on GitHub.

node tools/build.js -t node
node tools/build.js -t browser :common
node tools/build.js -t cdn :common

See our building documentation for more information.

Requirements

Highlight.js works on all modern browsers and currently supported Node.js versions. You'll need the following software to contribute to the core library:

• Node.js >= 12.x
• npm >= 6.x

License

Highlight.js is released under the BSD License. See our LICENSE file for details.

Links

The official website for the library is https://highlightjs.org/.

Further in-depth documentation for the API and other topics is at http://highlightjs.readthedocs.io/.

A list of the Core Team and contributors can be found in the CONTRIBUTORS.md file.

Changelog

Version 11.10.0

CAVEATS / POTENTIALLY BREAKING CHANGES

• Drops support for Node 16.x, which is no longer supported by Node.js.

Core Grammars:

• enh(typescript) add support for satisfies operator [Kisaragi Hiu][]
• enc(c) added more C23 keywords [Melkor-1][]
• enh(json) added jsonc as an alias [BackupMiles][]
• enh(gml) updated to latest language version (GML v2024.2) [gnysek][]
• enh(c) added more C23 keywords and preprcoessor directives [Eisenwave][]
• enh(js/ts) support namespaced tagged template strings [Aral Balkan][]
• enh(perl) fix false-positive variable match at end of string [Josh Goebel][]
• fix(cpp) not all kinds of number literals are highlighted correctly [Lê Duy Quang][]
• fix(css) fix overly greedy pseudo class matching [Bradley Mackey][]
• enh(arcade) updated to ArcGIS Arcade version 1.24 [Kristian Ekenes][]
• fix(typescript): params types [Mohamed Ali][]
• fix(rust) fix escaped double quotes in string [Mohamed Ali][]
• fix(rust) fix for r# raw identifier not being highlighted correctly. [JaeBaek Lee][]
• enh(rust) Adding union to be recognized as a keyword in Rust. [JaeBaek Lee][]
• fix(yaml) fix for yaml with keys having brackets highlighted incorrectly [Aneesh Kulkarni][]
• fix(csharp) add raw string highlighting for C# 11. [Tara][]
• fix(bash) fix # within token being detected as the start of a comment [Felix Uhl][]
• fix(python) fix or conflicts with string highlighting [Mohamed Ali][]
• enh(python) adds a scope to the self variable [Lee Falin][]
• enh(delphi) allow digits to be omitted for hex and binary literals [Jonah Jeleniewski][]
• enh(delphi) add support for digit separators [Jonah Jeleniewski][]
• enh(delphi) add support for character strings with non-decimal numerics [Jonah Jeleniewski][]
• fix(javascript) incorrect function name highlighting [CY Fung][]
• fix(1c) fix escaped symbols "+-;():=,[]" literals [Vitaly Barilko][]
• fix(swift) correctly highlight generics and conformances in type definitions [Bradley Mackey][]
• enh(swift) add package keyword [Bradley Mackey][]
• fix(swift) ensure keyword attributes highlight correctly [Bradley Mackey][]
• fix(types) fix interface LanguageDetail > keywords [Patrick Chiu]
• enh(java) add goto to be recognized as a keyword in Java [Alvin Joy][]
• enh(bash) add keyword sudo [Alvin Joy][]
• fix(haxe) captures new keyword without capturing it within variables/class names [Cameron Taylor][]
• fix(go) fix go number literals to accept _ separators, add hex p exponents [Lisa Ugray][]
• enh(markdown) add entity support [David Schach][] [TaraLei][]
• enh(css) add justify-items and justify-self attributes [Vasily Polovnyov][]
• enh(css) add accent-color, appearance, color-scheme, rotate, scale and translate attributes [Carl Räfting][]
• fix(fortran) fixes parsing of keywords delimited by dots [Julien Bloino][]
• enh(css) add select, option, optgroup, picture and source to list of known tags [Vasily Polovnyov][]
• enh(css) add inset, inset-*, border-start-*-radius and border-end-*-radius attributes [Vasily Polovnyov][]
• enh(css) add text-decoration-skip-ink, text-decoration-thickness and text-underline-offset attributes [Vasily Polovnyov][]
• enh(java) add when to be recognized as a keyword in Java [Chiel van de Steeg][]

New Grammars:

• added 3rd party CODEOWNERS grammar to SUPPORTED_LANGUAGES [nataliia-radina][]
• added 3rd party Luau grammar to SUPPORTED_LANGUAGES [Robloxian Demo][]
• added 3rd party ReScript grammar to SUPPORTED_LANGUAGES [Paul Tsnobiladzé][]
• added 3rd party Zig grammar to SUPPORTED_LANGUAGES [Hyou BunKen][]
• added 3rd party WGSL grammar to SUPPORTED_LANGUAGES [Arman Uguray][]
• added 3rd party Unison grammar to SUPPORTED_LANGUAGES [Rúnar Bjarnason][]
• added 3rd party Phix grammar to SUPPORTED_LANGUAGES [PeteLomax][]
• added 3rd party Mirth grammar to SUPPORTED_LANGUAGES [Sierra][]
• added 3rd party JSONata grammar to SUPPORTED_LANGUAGES [Vlad Dimov][]

Developer Tool:

• enh(tools): order CSS options picklist [David Schach][]
• enh(tools): remove duplicate CSS options [David Schach][]
• (typescript): deprecate old highlight API [Misha Kaletsky][]

Themes:

• Added 1c-light theme a like in the IDE 1C:Enterprise 8 (for 1c) [Vitaly Barilko][]