🎨 react-shiki

A performant client-side syntax highlighting component and hook for React, built with Shiki.

See the demo page with highlighted code blocks showcasing several Shiki themes!

🎨 react-shiki

Features

🖼️ Provides both a ShikiHighlighter component and a useShikiHighlighter hook for more flexibility
🔐 Flexible output: Choose between React elements (no dangerouslySetInnerHTML) or HTML strings
📦 Multiple bundle options: Full bundle (~1.2MB gz), web bundle (~707KB gz), or minimal core bundle for fine-grained bundle control
🖌️ Full support for custom TextMate themes and languages
🧬 Automatic highlighting of embedded languages (e.g. TypeScript fenced inside Markdown) via Shiki's guessEmbeddedLanguages
🔧 Supports passing custom Shiki transformers to the highlighter, in addition to all other options supported by codeToHast
🚰 Performant highlighting of streamed code, with optional throttling
📚 Includes minimal default styles for code blocks
🚀 Shiki dynamically imports only the languages and themes used on a page for optimal performance
🖥️ ShikiHighlighter component displays a language label for each code block when showLanguage is set to true (default)
🎨 Customizable styling of generated code blocks and language labels
📏 Optional line numbers with customizable starting number and styling

Installation

npm i react-shiki

Usage

You can use either the ShikiHighlighter component or the useShikiHighlighter hook to highlight code.

Using the Component:

import ShikiHighlighter from "react-shiki";

function CodeBlock() {
  return (
    <ShikiHighlighter language="jsx" theme="ayu-dark">
      {code.trim()}
    </ShikiHighlighter>
  );
}

Using the Hook:

import { useShikiHighlighter } from "react-shiki";

function CodeBlock({ code, language }) {
  const highlightedCode = useShikiHighlighter(code, language, "github-dark");

  return <div className="code-block">{highlightedCode}</div>;
}

Bundle Options

react-shiki, like shiki, offers three entry points to balance convenience and bundle optimization:

`react-shiki` (Full Bundle)

import ShikiHighlighter from 'react-shiki';

Size: ~6.4MB minified, ~1.2MB gzipped (includes ~12KB react-shiki)
Languages: All Shiki languages and themes
Exported engines: createJavaScriptRegexEngine, createJavaScriptRawEngine
Use case: Unknown language requirements, maximum language support
Setup: Zero configuration required

`react-shiki/web` (Web Bundle)

import ShikiHighlighter from 'react-shiki/web';

Size: ~3.8MB minified, ~707KB gzipped (includes ~12KB react-shiki)
Languages: Web-focused languages (HTML, CSS, JS, TS, JSON, Markdown, Vue, JSX, Svelte)
Exported engines: createJavaScriptRegexEngine, createJavaScriptRawEngine
Use case: Web applications with balanced size/functionality
Setup: Drop-in replacement for main entry point

`react-shiki/core` (Minimal Bundle)

import ShikiHighlighter, { 
  createHighlighterCore,        // re-exported from shiki/core
  createOnigurumaEngine,        // re-exported from shiki/engine/oniguruma
  createJavaScriptRegexEngine,  // re-exported from shiki/engine/javascript
} from 'react-shiki/core';

// Create custom highlighter with dynamic imports to optimize client-side bundle size
const highlighter = await createHighlighterCore({
  themes: [import('@shikijs/themes/nord')],
  langs: [import('@shikijs/langs/typescript')],
  engine: createOnigurumaEngine(import('shiki/wasm')) 
    // or createJavaScriptRegexEngine()
});

<ShikiHighlighter highlighter={highlighter} language="typescript" theme="nord">
  {code}
</ShikiHighlighter>

Size: ~12KB + your imported themes/languages
Languages: User-defined via custom highlighter
Use case: Production apps requiring maximum bundle control
Setup: Requires custom highlighter configuration
Engine options: Choose JavaScript engine (smaller bundle, faster startup) or Oniguruma (WASM, maximum language support)

RegExp Engines

Shiki offers three built-in engines for syntax highlighting:

Oniguruma - Default engine using compiled WebAssembly, offers maximum language support
JavaScript RegExp - Smaller bundle, faster startup, compiles patterns on-the-fly, recommended for client-side highlighting
JavaScript Raw - For pre-compiled languages, skips transpilation step for best performance

Using Engines with Full and Web Bundles

The full and web bundles use Oniguruma by default, but you can override this with the engine option:

import {
  useShikiHighlighter,
  createJavaScriptRegexEngine,
  createJavaScriptRawEngine
} from 'react-shiki';

// Hook with JavaScript RegExp engine
const highlightedCode = useShikiHighlighter(code, 'typescript', 'github-dark', {
  engine: createJavaScriptRegexEngine()
});

// Component with JavaScript Raw engine (for pre-compiled languages)
// See https://shiki.style/guide/regex-engines#pre-compiled-languages
<ShikiHighlighter
  language="typescript"
  theme="github-dark"
  engine={createJavaScriptRawEngine()}
>
  {code}
</ShikiHighlighter>

Using Engines with Core Bundle

When using the core bundle, you must specify an engine:

import {
  createHighlighterCore,
  createOnigurumaEngine,
  createJavaScriptRegexEngine
} from 'react-shiki/core';

const highlighter = await createHighlighterCore({
  themes: [import('@shikijs/themes/nord')],
  langs: [import('@shikijs/langs/typescript')],
  engine: createJavaScriptRegexEngine() // or createOnigurumaEngine(import('shiki/wasm'))
});

Engine Options

The JavaScript RegExp engine is strict by default. For best-effort results with unsupported grammars, enable the forgiving option:

createJavaScriptRegexEngine({ forgiving: true });

See Shiki - RegExp Engines for more info.

Configuration

Common Configuration Options

Option	Type	Default	Description
`code`	`string`	-	Code to highlight
`language`	`string \| object`	-	Language to highlight, built-in or custom TextMate grammar object
`theme`	`string \| object`	`'github-dark'`	Single or multi-theme configuration, built-in or custom TextMate theme object
`delay`	`number`	`0`	Delay between highlights (in milliseconds)
`customLanguages`	`array`	`[]`	Deprecated: use `preloadLanguages` instead.
`preloadLanguages`	`array`	`[]`	Preload bundled language IDs and custom language grammars
`langAlias`	`object`	`{}`	Map of language aliases
`engine`	`RegexEngine`	Oniguruma	RegExp engine for syntax highlighting (Oniguruma, JavaScript RegExp, or JavaScript Raw)
`showLineNumbers`	`boolean`	`false`	Display line numbers alongside code
`startingLineNumber`	`number`	`1`	Starting line number when line numbers are enabled
`highlightLineNumbers`	`number[]`	-	Displayed line numbers to highlight
`transformers`	`array`	`[]`	Custom Shiki transformers for modifying the highlighting output
`cssVariablePrefix`	`string`	`'--shiki'`	Prefix for CSS variables storing theme colors
`defaultColor`	`string \| false`	`'light'`	Default theme mode when using multiple themes, can also disable default theme
`outputFormat`	`string`	`'react'`	Output format: 'react' for React nodes, 'html' for HTML string, or 'tokens' for Shiki tokens (hook only, experimental)
`tabindex`	`number`	`0`	Tab index for the code block
`decorations`	`array`	`[]`	Custom decorations to wrap the highlighted tokens with
`structure`	`string`	`'classic'`	The structure of the generated HAST and HTML - `classic` or `inline`
`codeToHastOptions`	-	-	All other options supported by Shiki's `codeToHast`

Component-specific Props

The ShikiHighlighter component offers minimal built-in styling and customization options out-of-the-box:

Prop	Type	Default	Description
`showLanguage`	`boolean`	`true`	Displays language label in top-right corner
`addDefaultStyles`	`boolean`	`true`	Adds minimal default styling to the highlighted code block
`as`	`string`	`'div'`	Component's Root HTML element
`className`	`string`	-	Custom class name for the code block
`langClassName`	`string`	-	Class name for styling the language label
`style`	`object`	-	Inline style object for the code block
`langStyle`	`object`	-	Inline style object for the language label

Embedded Language Highlighting

react-shiki uses Shiki's guessEmbeddedLanguages to automatically detect, load, and highlight languages nested inside other languages. For example, a TypeScript fenced code block inside a Markdown document will be highlighted as TypeScript without any extra configuration. Embedded languages are dynamically loaded on demand, as long as they exist in your bundle.

Multi-theme Support

To use multiple theme modes, pass an object with your multi-theme configuration to the theme prop in the ShikiHighlighter component:

<ShikiHighlighter
  language="tsx"
  theme={{
    light: "github-light",
    dark: "github-dark",
    dim: "github-dark-dimmed",
  }}
  defaultColor="dark"
>
  {code.trim()}
</ShikiHighlighter>

Or, when using the hook, pass it to the theme parameter:

const highlightedCode = useShikiHighlighter(
  code,
  "tsx",
  {
    light: "github-light",
    dark: "github-dark",
    dim: "github-dark-dimmed",
  },
  {
    defaultColor: "dark",
  }
);

Making Themes Reactive

There are two approaches to make multi-themes reactive to your site's theme:

Option 1: Using `light-dark()` Function (Recommended)

Set defaultColor="light-dark()" to use CSS's built-in light-dark() function. This automatically switches themes based on the user's color-scheme preference:

// Component
<ShikiHighlighter
  language="tsx"
  theme={{
    light: "github-light",
    dark: "github-dark",
  }}
  defaultColor="light-dark()"
>
  {code.trim()}
</ShikiHighlighter>

// Hook
const highlightedCode = useShikiHighlighter(code, "tsx", {
  light: "github-light",
  dark: "github-dark",
}, {
  defaultColor: "light-dark()"
});

Ensure your site sets the color-scheme CSS property:

:root {
  color-scheme: light dark;
}

/* Or dynamically for class based dark mode */
:root {
  color-scheme: light;
}

:root.dark {
  color-scheme: dark;
}

Option 2: CSS Theme Switching

For broader browser support or more control, add CSS snippets to your site to enable theme switching with media queries or class-based switching. See Shiki's documentation for the required CSS snippets.

Note: The light-dark() function requires modern browser support. For older browsers, use the manual CSS variables approach.

Custom Themes

Custom themes can be passed as a TextMate theme JavaScript object (example).

import tokyoNight from "../styles/tokyo-night.json";

// Component
<ShikiHighlighter language="tsx" theme={tokyoNight}>
  {code.trim()}
</ShikiHighlighter>

// Hook
const highlightedCode = useShikiHighlighter(code, "tsx", tokyoNight);

Custom Languages

Custom languages should be passed as a TextMate grammar JavaScript object (example).

import mcfunction from "../langs/mcfunction.tmLanguage.json";

// Component
<ShikiHighlighter language={mcfunction} theme="github-dark">
  {code.trim()}
</ShikiHighlighter>

// Hook
const highlightedCode = useShikiHighlighter(code, mcfunction, "github-dark");

Preloading Languages

If highlighting is dynamic at runtime, preload custom languages.

import mcfunction from "../langs/mcfunction.tmLanguage.json";
import bosque from "../langs/bosque.tmLanguage.json";

// Component
<ShikiHighlighter
  language="typescript"
  theme="github-dark"
  preloadLanguages={[mcfunction, bosque]}
>
  {code.trim()}
</ShikiHighlighter>

// Hook
const highlightedCode = useShikiHighlighter(code, "typescript", "github-dark", {
  preloadLanguages: [mcfunction, bosque],
});

Note

Bundled languages are loaded on demand and do not need to be preloaded.

Language Aliases

You can define custom aliases for languages using the langAlias option. This is useful when you need to support alternative names for languages:

// Component
<ShikiHighlighter 
  language="indents" 
  theme="github-dark" 
  langAlias={{ indents: "python" }}
>
  {code.trim()}
</ShikiHighlighter>

// Hook
const highlightedCode = useShikiHighlighter(code, "indents", "github-dark", {
  langAlias: { indents: "python" },
});

Custom Transformers

import { customTransformer } from "../utils/shikiTransformers";

// Component
<ShikiHighlighter language="tsx" transformers={[customTransformer]}>
  {code.trim()}
</ShikiHighlighter>

// Hook
const highlightedCode = useShikiHighlighter(code, "tsx", "github-dark", {
  transformers: [customTransformer],
});

Line Numbers

Line numbers are CSS-based and can be customized with CSS variables:

// Component
<ShikiHighlighter 
  language="javascript"
  theme="github-dark"
  showLineNumbers
  startingLineNumber={0} // default is 1
  highlightLineNumbers={[2, 4]}
>
  {code}
</ShikiHighlighter>

// Hook (import 'react-shiki/css' for line numbers to work)
const highlightedCode = useShikiHighlighter(code, "javascript", "github-dark", {
  showLineNumbers: true,
  startingLineNumber: 0,
  highlightLineNumbers: [2, 4],
});

Note

When using the hook with line numbers or highlighted lines, import the CSS file or provide your own CSS for .rs-line-number (line span), .rs-highlighted-line (line span), and .rs-has-line-numbers / .rs-has-highlighted-lines (container code element).

import 'react-shiki/css';

highlightLineNumbers uses displayed line numbers, so it works with startingLineNumber.

Component-internal default classes are namespaced under rs-* and written with zero-specificity :where() selectors, so they can't be clobbered by CSS resets (e.g. Tailwind preflight) regardless of stylesheet load order, while any rule in your own CSS — even a bare element selector — overrides them.

Available CSS variables for customization:

--rs-line-numbers-foreground: rgba(107, 114, 128, 0.5);
--rs-line-numbers-width: 2ch;
--rs-line-numbers-padding-left: 0ch;
--rs-line-numbers-padding-right: 2ch;
--rs-line-numbers-font-size: inherit;
--rs-line-numbers-font-weight: inherit;
--rs-line-numbers-opacity: 1;
--rs-highlighted-line-background: color-mix(in srgb, currentColor 10%, transparent);
--rs-highlighted-line-number-foreground: color-mix(in srgb, currentColor 65%, transparent);

With default styles, highlighted-line backgrounds automatically extend into the pre's horizontal padding, reaching the container edges. When styling the pre yourself, highlights cover the code content area.

You can customize them in your own CSS or by using the style prop on the component:

<ShikiHighlighter 
  language="javascript"
  theme="github-dark"
  showLineNumbers
  style={{
    '--rs-line-numbers-foreground': '#60a5fa',
    '--rs-line-numbers-width': '3ch'
  }}
>
  {code}
</ShikiHighlighter>

Integration

Integration with react-markdown

Create a component to handle syntax highlighting:

import ReactMarkdown from "react-markdown";
import ShikiHighlighter, { isInlineCode } from "react-shiki";

const CodeHighlight = ({ className, children, node, ...props }) => {
  const code = String(children).trim();
  const match = className?.match(/language-(\w+)/);
  const language = match ? match[1] : undefined;
  const isInline = node ? isInlineCode(node) : undefined;

  return !isInline ? (
    <ShikiHighlighter language={language} theme="github-dark" {...props}>
      {code}
    </ShikiHighlighter>
  ) : (
    <code className={className} {...props}>
      {code}
    </code>
  );
};

Pass the component to react-markdown as a code component:

<ReactMarkdown
  components={{
    code: CodeHighlight,
  }}
>
  {markdown}
</ReactMarkdown>

Handling Inline Code

Prior to 9.0.0, react-markdown exposed the inline prop to code components which helped to determine if code is inline. This functionality was removed in 9.0.0. For your convenience, react-shiki provides two ways to replicate this functionality and API.

Method 1: Using the isInlineCode helper:

react-shiki exports isInlineCode which parses the node prop from react-markdown and identifies inline code by checking for the absence of newline characters:

import ShikiHighlighter, { isInlineCode } from "react-shiki";

const CodeHighlight = ({ className, children, node, ...props }) => {
  const match = className?.match(/language-(\w+)/);
  const language = match ? match[1] : undefined;

  const isInline = node ? isInlineCode(node) : undefined;

  return !isInline ? (
    <ShikiHighlighter language={language} theme="github-dark" {...props}>
      {String(children).trim()}
    </ShikiHighlighter>
  ) : (
    <code className={className} {...props}>
      {children}
    </code>
  );
};

Method 2: Using the rehypeInlineCodeProperty plugin:

react-shiki also exports rehypeInlineCodeProperty, a rehype plugin that adds an inline prop to react-markdown code components. It works by checking if <code> is nested within a <pre> tag; if not, it's considered inline code and the inline prop is set to true.

It's passed as a rehypePlugin to react-markdown:

import ReactMarkdown from "react-markdown";
import { rehypeInlineCodeProperty } from "react-shiki";

<ReactMarkdown
  rehypePlugins={[rehypeInlineCodeProperty]}
  components={{
    code: CodeHighlight,
  }}
>
  {markdown}
</ReactMarkdown>;

Now inline can be accessed as a prop in the code component:

const CodeHighlight = ({
  inline,
  className,
  children,
  node,
  ...props
}: CodeHighlightProps): JSX.Element => {
  const match = className?.match(/language-(\w+)/);
  const language = match ? match[1] : undefined;
  const code = String(children).trim();

  return !inline ? (
    <ShikiHighlighter language={language} theme="github-dark" {...props}>
      {code}
    </ShikiHighlighter>
  ) : (
    <code className={className} {...props}>
      {code}
    </code>
  );
};

Performance

Throttling Real-time Highlighting

To reduce highlighting work for frequently changing code:

// With the component
<ShikiHighlighter language="tsx" theme="github-dark" delay={150}>
  {code.trim()}
</ShikiHighlighter>

// With the hook
const highlightedCode = useShikiHighlighter(code, "tsx", "github-dark", {
  delay: 150,
});

Output Formats

react-shiki can return highlighted code in three formats:

React Nodes (Default) - Rendered as React elements, no dangerouslySetInnerHTML required

// Hook
const highlightedCode = useShikiHighlighter(code, "tsx", "github-dark");

// Component
<ShikiHighlighter language="tsx" theme="github-dark">
  {code}
</ShikiHighlighter>

HTML String - Rendered via dangerouslySetInnerHTML

// Hook (returns HTML string, use dangerouslySetInnerHTML to render)
const highlightedCode = useShikiHighlighter(code, "tsx", "github-dark", {
  outputFormat: 'html'
});

// Component (automatically uses dangerouslySetInnerHTML when outputFormat is 'html')
<ShikiHighlighter language="tsx" theme="github-dark" outputFormat="html">
  {code}
</ShikiHighlighter>

Shiki Tokens (Experimental) - Hook-only output for custom renderers

const highlighted = useShikiHighlighter(code, "tsx", "github-dark", {
  outputFormat: "tokens",
});

const rendered = highlighted?.tokens.map((line, i) => (
  <div key={i}>
    {line.map((token, j) => (
      <span key={j} style={{ color: token.color }}>
        {token.content}
      </span>
    ))}
  </div>
));

The React and HTML formats spend their rendering work in different phases. HTML output skips per-token React element creation and reconciliation, reducing render-phase overhead for large, one-shot highlights, but each update replaces the code block's entire DOM subtree via innerHTML. React output pays for element creation and diffing on every update, but commits only incremental DOM mutations, minimizing DOM churn for frequently re-highlighted code such as streaming LLM output.

HTML output hands the highlighted markup to the DOM via dangerouslySetInnerHTML, so only use it with trusted code sources. The default React output is the safe choice for untrusted content.

Token output is for when you need to own rendering yourself; it is intentionally available on the hook, not the ShikiHighlighter component, since react-shiki's markup-based features no longer apply once you control the markup. Note that Shiki's codeToTokens does not run transformers or decorations, so markup-producing options, including transformers, decorations, line numbers, and structure, have no effect on token output.

Made with ❤️ by Bassim (AVGVSTVS96)

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🎨 react-shiki

Features

Installation

Usage

Bundle Options

react-shiki (Full Bundle)

react-shiki/web (Web Bundle)

react-shiki/core (Minimal Bundle)

RegExp Engines

Using Engines with Full and Web Bundles

Using Engines with Core Bundle

Engine Options

Configuration

Common Configuration Options

Component-specific Props

Embedded Language Highlighting

Multi-theme Support

Making Themes Reactive

Option 1: Using light-dark() Function (Recommended)

Option 2: CSS Theme Switching

Custom Themes

Custom Languages

Preloading Languages

Language Aliases

Custom Transformers

Line Numbers

Integration

Integration with react-markdown

Handling Inline Code

Performance

Throttling Real-time Highlighting

Output Formats

About

Topics

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License

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Languages

`react-shiki` (Full Bundle)

`react-shiki/web` (Web Bundle)

`react-shiki/core` (Minimal Bundle)

Option 1: Using `light-dark()` Function (Recommended)