Rehype Pretty Code
rehype-pretty-code
is a Rehype plugin
powered by the shiki
syntax highlighter that provides beautiful code blocks for Markdown or MDX. It works on both the server at build-time (avoiding runtime syntax highlighting) and on the client for dynamic highlighting.
Editor-Grade Highlighting
Enjoy the accuracy and granularity of VS Code’s syntax highlighting engine and the popularity of its themes ecosystem - use any VSCode theme you want!
Line Numbers and Line Highlighting
Draw attention to a particular line of code.
import { useFloating } from "@floating-ui/react";
function MyComponent() {
const { refs, floatingStyles } = useFloating();
return (
<>
<div ref={refs.setReference} />
<div ref={refs.setFloating} style={floatingStyles} />
</>
);
}
Word Highlighting
Draw attention to a particular word or series of characters.
import { useFloating } from "@floating-ui/react";
function MyComponent() {
const { refs, floatingStyles } = useFloating();
return (
<>
<div ref={refs.setReference} />
<div ref={refs.setFloating} style={floatingStyles} />
</>
);
}
Inline Code Highlighting
The result of [1, 2, 3].join('-')
is '1-2-3'
.
Context Aware Inline Code
For instance, if you had the following code block:
function getStringLength(str) {
return str.length;
}
When we refer to getStringLength
as a plain variable,
we can color it as a function. Same with function
, or
str
vs. str
, etc. This allows
you to semantically tie inline code with the nearest code block it’s referring
to.
ANSI Highlighting
vite v5.0.0 dev server running at:
> Local: http://localhost:3000/
> Network: use `--host` to expose
ready in 125ms.
8:38:02 PM [vite] hmr update /src/App.jsx
Inline ANSI: > Local: http://localhost:3000/
Installation
Install via your terminal:
npm install rehype-pretty-code shiki
pnpm add rehype-pretty-code shiki
bun add rehype-pretty-code shiki
yarn add rehype-pretty-code shiki
This package is ESM-only and currently supports shiki
^1.0.0
.
To use the latest version in Next.js, ensure your config file is
ESM
:next.config.mjs
. Here’s a full example: rehype-pretty-code/examples/next/next.config.mjs
Usage
The following works both on the server and on the client.
import { unified } from "unified";
import remarkParse from "remark-parse";
import remarkRehype from "remark-rehype";
import rehypeStringify from "rehype-stringify";
import rehypePrettyCode from "rehype-pretty-code";
async function main() {
const file = await unified()
.use(remarkParse)
.use(remarkRehype)
.use(rehypePrettyCode, {
// See Options section below.
})
.use(rehypeStringify)
.process("`const numbers = [1, 2, 3]{:js}`");
console.log(String(file));
}
main();
Note that unified
v11 is used as a dependency internally.
Ensure your unified
version is compatible.
MDX
The following example shows how to use this package with Next.js.
import nextMDX from "@next/mdx";
import rehypePrettyCode from "rehype-pretty-code";
/** @type {import('rehype-pretty-code').Options} */
const options = {
// See Options section below.
};
const withMDX = nextMDX({
extension: /\.mdx?$/,
options: {
remarkPlugins: [],
rehypePlugins: [[rehypePrettyCode, options]],
},
});
/** @type {import('next').NextConfig} */
const nextConfig = { reactStrictMode: true };
export default withMDX(nextConfig);
Disable the mdxRs
option if Rehype plugins do not work.
Styles
This library is unstyled. This means it does not provide a CSS file that applies styling by default. Rather, it provides logical attributes that you use to apply the styling yourself.
For instance, the following CSS prevents overflow and adds padding:
pre {
overflow-x: auto;
padding: 1rem 0;
}
pre [data-line] {
padding: 0 1rem;
}
Features including highlighted lines, chars, and line numbers expose data attributes that enable you to add your own styling, which are explained below.
Options
interface Options {
grid?: boolean;
theme?: Theme | Record<string, Theme>;
keepBackground?: boolean;
bypassInlineCode?: boolean;
defaultLang?: string | { block?: string; inline?: string };
tokensMap?: Record<string, string>;
transformers?: ShikiTransformer[];
filterMetaString?(str: string): string;
getHighlighter?(options: BundledHighlighterOptions): Promise<Highlighter>;
onVisitLine?(element: LineElement): void;
onVisitHighlightedLine?(element: LineElement): void;
onVisitHighlightedChars?(element: CharsElement, id: string | undefined): void;
onVisitTitle?(element: Element): void;
onVisitCaption?(element: Element): void;
}
grid
A grid style is present by default which allows line highlighting to span the entire width of a horizontally-scrollable code block.
You can disable this setting if necessary:
const options = {
grid: false,
};
theme
The default theme is github-dark-dimmed
. Shiki has a bunch of
pre-packaged themes,
which can be specified as a plain string:
const options = {
theme: "one-dark-pro",
};
You can use your own theme as well by passing the theme JSON:
const options = {
theme: JSON.parse(fs.readFileSync("./themes/moonlight-ii.json", "utf-8")),
};
keepBackground
To apply a custom background instead of inheriting the background from the theme:
const options = {
keepBackground: false,
};
bypassInlineCode
Skip inline code highlighting:
const options = {
bypassInlineCode: true,
};
defaultLang
When no code language is specified, inline code or code blocks will not be themed (nor will the background), which may appear incongruous with others.
In this case, you can specify a default language:
const options = {
defaultLang: "plaintext",
};
Or you can also specify default languages for inline code and code blocks separately:
const options = {
defaultLang: {
block: "plaintext",
inline: "plaintext",
},
};
transformers
Transformers are a
Shiki-native way to manipulate the hAST
tree of the code blocks and further
extend the behavior of this plugin. The
@shikijs/transformers
package provides some useful transformers.
import { transformerNotationDiff } from '@shikijs/transformers';
const options = {
transformers: [transformerNotationDiff()],
};
Meta Strings
Code blocks are configured via the meta string on the top codeblock fence.
If your library also parses code blocks’ meta strings, it may cause conflicts with
rehype-pretty-code
. This option allows you to filter out some part of the meta string before the library starts parsing it.const options = { filterMetaString: (string) => string.replace(/filename="[^"]*"/, ""), };
Highlight Lines
Place a numeric range inside {}
.
```js {1-3,4}
```
Styling: The line <span>
receives a data-highlighted-line
attribute that enables you to style via CSS.
Group Highlighted Lines By Id
Place an id after #
after the {}
. This allows you to color or style lines
differently based on their id.
```js {1,2}#a {3,4}#b
```
Styling: The line <span>
receives a
data-highlighted-line-id="<id>"
attribute that enables you to style via CSS.
Highlight Chars
You can use either /
:
```js /carrot/
```
Or "
as a delimiter:
```js "carrot"
```
Different segments of chars can also be highlighted:
```js /carrot/ /apple/
```
Styling: The chars <span>
receives a data-highlighted-chars
attribute to style via CSS.
To highlight only the third to fifth instances of carrot
, a numeric range can
be placed after the last /
.
```js /carrot/3-5
```
Highlight only the third to fifth instances of carrot
and any instances of
apple
.
```js /carrot/3-5 /apple/
```
Group Highlighted Chars By Id
Place an id after #
after the chars. This allows you to color chars
differently based on their id.
```js /age/#v /name/#v /setAge/#s /setName/#s /50/#i /"Taylor"/#i
const [age, setAge] = useState(50);
const [name, setName] = useState("Taylor");
```
const [age, setAge] = useState(50);
const [name, setName] = useState("Taylor");
Styling: The chars <span>
receives a data-chars-id="<id>"
attribute to style via CSS.
Highlight Inline Code
Append {:lang}
(e.g. {:js}
) to the end of inline code to highlight it like
a regular code block.
This is an array `[1, 2, 3]{:js}` of numbers 1 through 3.
Highlight Plain Text
Append {:.token}
to the end of the inline code to highlight it based on a
token specified in your VS Code theme. Tokens start with a .
to differentiate
them from a language.
The name of the function is `getStringLength{:.entity.name.function}`.
You can create a map of tokens to shorten this usage throughout your docs:
const options = {
tokensMap: {
fn: "entity.name.function",
},
};
The name of the function is `getStringLength{:.fn}`.
Titles
Add a file title to your code block, with text inside double quotes (""
):
```js title="..."
```
Captions
Add a caption underneath your code block, with text inside double quotes (""
):
```js caption="..."
```
Line Numbers
CSS counters can be used to add line numbers.
code[data-line-numbers] {
counter-reset: line;
}
code[data-line-numbers] > [data-line]::before {
counter-increment: line;
content: counter(line);
/* Other styling */
display: inline-block;
width: 0.75rem;
margin-right: 2rem;
text-align: right;
color: gray;
}
code[data-line-numbers-max-digits="2"] > [data-line]::before {
width: 1.25rem;
}
code[data-line-numbers-max-digits="3"] > [data-line]::before {
width: 1.75rem;
}
code[data-line-numbers-max-digits="4"] > [data-line]::before {
width: 2.25rem;
}
If you want to conditionally show them, use showLineNumbers
:
```js showLineNumbers
```
Styling: <code>
will have attributes data-line-numbers
and
data-line-numbers-max-digits="n"
.
If you want to start line numbers at a specific number, use
showLineNumbers{number}
:
```js showLineNumbers{number}
```
Multiple Themes (Dark and Light Mode)
Pass your themes to theme
, where the keys represent
the color mode:
const options = {
theme: {
dark: "github-dark-dimmed",
light: "github-light",
},
};
Now, use the following CSS to display the variable colors ââŹâ if a space is found in the theme name, then CSS variable keys based on the object are available (more info):
code[data-theme*=" "],
code[data-theme*=" "] span {
color: var(--shiki-light);
background-color: var(--shiki-light-bg);
}
@media (prefers-color-scheme: dark) {
code[data-theme*=" "],
code[data-theme*=" "] span {
color: var(--shiki-dark);
background-color: var(--shiki-dark-bg);
}
}
The <code>
and <pre>
elements will have the data attribute
data-theme="...themes"
, listing each theme value space-separated:
<code data-theme="github-dark-dimmed github-light"></code>
Visitor Hooks
To customize the HTML output, you can use visitor callback hooks to manipulate the hAST elements directly:
const options = {
onVisitLine(element) {
console.log("Visited line");
},
onVisitHighlightedLine(element) {
console.log("Visited highlighted line");
},
onVisitHighlightedChars(element) {
console.log("Visited highlighted chars");
},
onVisitTitle(element) {
console.log("Visited title");
},
onVisitCaption(element) {
console.log("Visited caption");
},
};
Custom Highlighter
To completely configure the highlighter, use the
getHighlighter
option. This is helpful if you’d like
to configure other Shiki options, such as langs
.
import { getHighlighter } from "shiki";
const options = {
getHighlighter: (options) =>
getHighlighter({
...options,
langs: [
"plaintext",
async () => JSON.parse(await readFile("my-grammar.json", "utf-8")),
],
}),
};
React Server Component
The usage works directly in React Server Components. Here’s an example:
import * as React from "react";
import { unified } from "unified";
import remarkParse from "remark-parse";
import remarkRehype from "remark-rehype";
import rehypeStringify from "rehype-stringify";
import rehypePrettyCode from "rehype-pretty-code";
export async function Code({ code }: { code: string }) {
const highlightedCode = await highlightCode(code);
return (
<section
dangerouslySetInnerHTML={{
__html: highlightedCode,
}}
/>
);
}
async function highlightCode(code: string) {
const file = await unified()
.use(remarkParse)
.use(remarkRehype)
.use(rehypePrettyCode, {
keepBackground: false,
})
.use(rehypeStringify)
.process(code);
return String(file);
}
Then, import the RSC into a page or another component:
import * as React from "react";
import { Code } from "./code.tsx";
export default async function Page() {
return (
<main>
<Code code="`const numbers = [1, 2, 3]{:js}`" />
</main>
);
}