🎨 react-shiki

[!NOTE] This library is still in development. More features will be implemented, and the API may change. Contributions are welcome!

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
  • Installation
  • Usage
    • Common Configuration Options
    • Component-specific Props
    • Integration with react-markdown
    • Handling Inline Code
    • Multi-theme Support
    • Custom Themes
    • Custom Languages
      • Preloading Custom Languages
    • Custom Transformers
  • Performance
  • Throttling Real-time Highlighting
  • Streaming and LLM Chat UI

Features

• 🖼️ Provides both a ShikiHighlighter component and a useShikiHighlighter hook for more flexibility
• 🔐 No dangerouslySetInnerHTML - output from Shiki is parsed using html-react-parser
• 📦 Supports all built-in Shiki languages and themes
• 🖌️ Full support for custom TextMate themes and languages
• 🔧 Supports passing custom Shiki transformers to the highlighter
• 🚰 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

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>;
}

Common Configuration Options

| Option | Type | Default | Description | | ------------------- | ------------------ | --------------- | ------------------------------------------------------------------------- | | code | string | - | Code to highlight | | language | string \| object | - | Language to highlight, built-in or custom textmate grammer 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) | | transformers | array | [] | Custom Shiki transformers for modifying the highlighting output | | customLanguages | array | [] | Array of custom languages to preload | | 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 |

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 | 'pre' | 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 |

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

Method 1: Using the isInlineCode helper:

There are two ways to check if a code block is inline, both provide the same result: react-shiki exports isInlineCode which parses the node prop (from react-markdown) to determine if the code is inline:

import { isInlineCode, ShikiHighlighter } 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 rehype plugin:

react-shiki also exports rehypeInlineCodeProperty, a rehype plugin that adds an inline property to react-markdown to determine if code is inline based on the presence of a <pre> tag as a parent of <code>.

It's passed as a rehype plugin 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 CodeHighlight 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>
  );
};

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",
  }
);

See shiki's documentation for more information on dual and multi theme support, and for the CSS needed to make the themes reactive to your site's theme.

Custom Themes

Custom themes can be passed as a TextMate theme in JavaScript object. For example, it should look like this.

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

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

// Using the hook
const highlightedCode = useShikiHighlighter(code, "tsx", tokyoNight);

Custom Languages

Custom languages should be passed as a TextMate grammar in JavaScript object. For example, it should look like this

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

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

// Using the hook
const highlightedCode = useShikiHighlighter(code, mcfunction, "github-dark");

Preloading Custom Languages

For dynamic highlighting scenarios where language selection happens at runtime:

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

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

// With the hook
const highlightedCode = useShikiHighlighter(code, "typescript", "github-dark", {
  customLanguages: [mcfunction, bosque],
});

Custom Transformers

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

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

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

Performance

Throttling Real-time Highlighting

For improved performance when highlighting 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,
});

Streaming and LLM Chat UI

react-shiki can be used to highlight streamed code from LLM responses in real-time.

I use it for an LLM chatbot UI, it renders markdown and highlights code in memoized chat messages.

Using useShikiHighlighter hook:

import type { ReactNode } from "react";
import { isInlineCode, useShikiHighlighter, type Element } from "react-shiki";
import tokyoNight from "@styles/tokyo-night.mjs";

interface CodeHighlightProps {
  className?: string | undefined;
  children?: ReactNode | undefined;
  node?: Element | undefined;
}

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

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

  const highlightedCode = useShikiHighlighter(code, language, tokyoNight, {
    delay: 150,
  });

  return !isInline ? (
    <div
      className="shiki not-prose relative [&_pre]:overflow-auto 
      [&_pre]:rounded-lg [&_pre]:px-6 [&_pre]:py-5"
    >
      {language ? (
        <span
          className="absolute right-3 top-2 text-xs tracking-tighter
          text-muted-foreground/85"
        >
          {language}
        </span>
      ) : null}
      {highlightedCode}
    </div>
  ) : (
    <code className={className} {...props}>
      {children}
    </code>
  );
};

Or using the ShikiHighlighter component:

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

interface CodeHighlightProps {
  className?: string | undefined;
  children?: ReactNode | undefined;
  node?: Element | undefined;
}

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

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

  return !isInline ? (
    <ShikiHighlighter
      language={language}
      theme="github-dark"
      delay={150}
      {...props}
    >
      {code}
    </ShikiHighlighter>
  ) : (
    <code className={className}>{code}</code>
  );
};

Passed to react-markdown as a code component in memo-ized chat messages:

const RenderedMessage = React.memo(({ message }: { message: Message }) => (
  <div className={cn(messageStyles[message.role])}>
    <ReactMarkdown components={{ code: CodeHighlight }}>
      {message.content}
    </ReactMarkdown>
  </div>
));

export const ChatMessages = ({ messages }: { messages: Message[] }) => {
  return (
    <div className="space-y-4">
      {messages.map((message) => (
        <RenderedMessage key={message.id} message={message} />
      ))}
    </div>
  );
};