Twoslash

Usage

Thanks to the Twoslash integration of Shiki, the default code syntax highlighter, it is as simple as adding a transformer.

npm install fumadocs-twoslash twoslash

For Next.js, you need to externalize the following deps:

next.config.mjs (Next.js)

const config = {
  reactStrictMode: true,
  serverExternalPackages: ['typescript', 'twoslash'],
};

Add to your Shiki transformers.

source.config.ts (Fumadocs MDX)

import { defineConfig } from 'fumadocs-mdx/config';
import { transformerTwoslash } from 'fumadocs-twoslash';
import { rehypeCodeDefaultOptions } from 'fumadocs-core/mdx-plugins';

export default defineConfig({
  mdxOptions: {
    rehypeCodeOptions: {
      themes: {
        light: 'github-light',
        dark: 'github-dark',
      },
      transformers: [...(rehypeCodeDefaultOptions.transformers ?? []), transformerTwoslash()],

      // important: Shiki doesn't support lazy loading languages for codeblocks in Twoslash popups
      // make sure to define them first (e.g. the common ones)
      langs: ['js', 'jsx', 'ts', 'tsx'],
    },
  },
});

Add styles, Tailwind CSS v4 is required.

Tailwind CSS

@import 'fumadocs-twoslash/twoslash.css';

Add MDX components.

components/mdx.tsx

import * as Twoslash from 'fumadocs-twoslash/ui';
import defaultComponents from 'fumadocs-ui/mdx';
import type { MDXComponents } from 'mdx/types';

export function getMDXComponents(components?: MDXComponents) {
  return {
    ...defaultComponents,
    ...Twoslash,
    ...components,
  } satisfies MDXComponents;
}

Now you can add twoslash meta string to codeblocks.

```ts twoslash
console.log('Hello World');
```

Cache

Optionally, you can enable filesystem cache with typesCache option:

source.config.ts

import {  } from 'fumadocs-twoslash';
import {  } from 'fumadocs-twoslash/cache-fs';

({
  : (),
});

Example

Learn more about Twoslash notations.

Test

.ggroup
groupCollapsed
groupEnd;

const player:  = { : 'Hello World' };       
const player: Player

const  = '123';

.();

const  = '123';

a = 132;Cannot assign to 'a' because it is a constant.

Usage

Cache

Example

On this page