rehype-highlighter

rehype-highlighter is a rehype plugin that brings your Markdown code blocks to life with beautiful syntax highlighting.
It uses Shiki under the hood to highlight both fenced code blocks and inline code snippets.

Installation

Get ready to add some flair to your docs by installing rehype-highlighter!

• pnpm
  pnpm add -D rehype-highlighter
• npm
  npm install -D rehype-highlighter
• yarn
  yarn add -D rehype-highlighter

How it works

rehype-highlighter will scan through your markdown document and look for code blocks. When it finds a code block(whether fenced or inline), it will highlight it with Shiki to make it pop!

For fenced code blocks, it will wrap the highlighted code like this:

<pre
	class="rehype-highlighter"
	data-rh-highlighter-theme="theme"
><code><!--SHIKI-HIGHLIGHTED CODE--></code></pre>

For inline code, it will wrap it like this:

<code class="rehype-highlighter" data-rh-highlighter-inline data-rh-highlighter-theme="theme"
	><!--SHIKI-HIGHLIGHTED CODE--></code
>

This way, you can target the classes or attributes with your CSS and provide additional styling, or to toggle code blocks.

Highlight Inline Code

You can also easily highlight inline code snippets to spice up your docs. Simply precede the inline code with :language: where language is the programming language to highlight it as.

For example, to highlight import time from time in Python:

:python:import time from time

Escape Highlighting

If you actually want to show an inline code snippet without highlighting, just add a space before the first colon:

:js:console.log("")

The space will be removed but will prevent highlighting.

rehype-highlighter makes it easy to add beautiful, readable syntax highlighting to your Markdown code. Now your documentation can be informative AND stylish!

Usage

In order to use this plugin, you need to add it to your list of rehype plugins.

Here's one example on how you can set it up.

import { unified } from "unified";
import remarkParse from "remark-parse";
import remarkRehype from "remark-rehype";
import rehypeHighlighter from "rehype-highlighter";
import rehypeStringify from "rehype-stringify";

const processor = await unified()
	.use(remarkParse)
	.use(remarkRehype)
	.use(rehypeHighlighter)
	.use(rehypeStringify)
	.process("YOUR MARKDOWN CODE");

If you're using Mdsvex with Svelte

import { defineMDSveXConfig as defineConfig } from "mdsvex";
import rehypeHighlighter from "rehype-highlighter";

const config = defineConfig({
	extensions: [".md"],
	rehypePlugins: [rehypeHighlighter]
});

And that's all.

Options

There are a bunch of options which you can use with this plugin.
You just need to pass in an object with the plugin.

options.theme
Type: string.

This option is used to set the theme which should be used to highlight your code. It can be any of the built in themes or you can also load your custom themes and specify the name here.

Example,

const processor = await unified()
	.use(remarkParse)
	.use(remarkRehype)
	.use(rehypeHighlighter, {
		theme: "dracula"
	})
	.use(rehypeStringify)
	.process("YOUR MARKDOWN CODE");

options.loadThemes
Type: object[]

This is the way to load themes which are not included in the Shiki package. Also, you can load as many themes as you want. Just pass in the object for the theme and it will be loaded. After adding a theme here, you can then use options.theme to select the theme which you added by using the name.

Example,

import { fileURLToPath } from "node:url";

const processor = await unified()
	.use(remarkParse)
	.use(remarkRehype)
	.use(rehypeHighlighter, {
		loadThemes: [
			JSON.parse(fileURLToPath(new URL("./themes/moonlight.json", import.meta.url))),
			JSON.parse(fileURLToPath(new URL("./themes/ayu-dark.json", import.meta.url)))
		]
	})
	.use(rehypeStringify)
	.process("YOUR MARKDOWN CODE");

Now, you can set the highlighter to use those themes by passing the name to options.theme.

options.inlineCode.theme
Type: string

This option allows you to set the theme for only inline code snippets. By default it inherits the theme from options.theme. Do note that if a value is set for this, it stops inheriting all the themes from options.theme.

For example, let's say you have this configuration structure.

const processor = await unified()
	.use(remarkParse)
	.use(remarkRehype)
	.use(rehypeHighlighter, {
		theme: ["dracula", "github-light"],
		inlineCode: {
			theme: "github-dark"
		}
	})
	.use(rehypeStringify)
	.process("YOUR MARKDOWN CODE");

The highlighter will only use github-dark for your inline code blocks.

options.inlineCode.spaceSubstitution
Type: Boolean (True or False)

This option only applies to inline code. Svelte strips multiple whitespaces from elements and this can affect how your code is rendered when you choose to highlight inline code. What this option does is that, when you set it to true, it replaces every whitespace with it's html entity &nbps;, this way, your whitespace is not stripped and it's rendered.