vercel__streamdown/apps/website/content/docs/cjk-support.mdx

---
title: CJK Language Support
description: Full support for Chinese, Japanese, and Korean text with proper emphasis formatting.
---

Streamdown includes built-in support for CJK (Chinese, Japanese, Korean) languages, ensuring that emphasis markers like bold and italic work correctly with ideographic punctuation. This is particularly important for AI-generated content, where language models naturally place emphasis markers around phrases that include or end with punctuation.

## The Problem

The CommonMark/GFM specification has a [limitation](https://github.com/commonmark/commonmark-spec/issues/650) where emphasis markers (`**` or `*`) adjacent to ideographic punctuation marks occasionally fail to be recognized. This causes formatting to break in CJK text:

```markdown
**この文は太字になりません（This won't be bolded）。**この文のせいで（It is due to this sentence）。
```

Without CJK-friendly parsing, the text above would render as plain text instead of bold because the closing `**` appears next to the Japanese period.

## The Solution

Streamdown uses the [remark-cjk-friendly](https://www.npmjs.com/package/remark-cjk-friendly) and [remark-cjk-friendly-gfm-strikethrough](https://www.npmjs.com/package/remark-cjk-friendly-gfm-strikethrough) plugins to handle CJK text properly. This plugin implements an improved parsing approach that correctly recognizes emphasis markers adjacent to ideographic punctuation.

## Supported Features

### Bold Text with Punctuation

Works correctly with all ideographic punctuation marks:

```markdown
**日本語の文章（括弧付き）。**この文が後に続いても大丈夫です。
**中文文本（带括号）。**这句子继续也没问题。
**한국어 구문(괄호 포함)**을 강조.
```

{/* The following lang="..." is crucial to ensure proper han character rendering */}

Japanese: <span lang="ja"><strong>日本語の文章（括弧付き）。</strong>この文が後に続いても大丈夫です。</span>

Chinese: <span lang="zh-Hans"><strong>中文文本（带括号）。</strong>这句子继续也没问题。</span>

Korean: <span lang="ko"><strong>한국어 구문(괄호 포함)</strong>을 강조.</span>

### Italic Text with Punctuation

```markdown
*これは斜体のテキストです（括弧付き）。*この文が後に続いても大丈夫です。
*这是斜体文字（带括号）。*这句子继续也没问题。
*이 텍스트(괄호 포함)*는 기울임꼴입니다.
```

Japanese: <span lang="ja"><em>これは斜体のテキストです（括弧付き）。</em>この文が後に続いても大丈夫です。</span>

Chinese: <span lang="zh-Hans"><em>这是斜体文字（带括号）。</em>这句子继续也没问题。</span>

Korean: <span lang="ko"><em>이 텍스트(괄호 포함)</em>는 기울임꼴입니다.</span>

### Strikethrough with Punctuation

Streamdown includes `remark-cjk-friendly-gfm-strikethrough` for proper strikethrough support:

```markdown
~~削除されたテキスト（括弧付き）。~~この文は正しいです。
~~删除的文字（带括号）。~~这个句子是正确的。
~~이 텍스트(괄호 포함)~~를 삭제합니다.
```

Japanese: <span lang="ja"><del>削除されたテキスト（括弧付き）。</del>この文は正しいです。</span>

Chinese: <span lang="zh-Hans"><del>删除的文字（带括号）。</del>这个句子是正确的。</span>

Korean: <span lang="ko"><del>이 텍스트(괄호 포함)</del>를 삭제합니다。</span>

### Mixed Content

CJK and English text work seamlessly together:

```markdown
**重要提示（Important Notice）：**请注意。
```

Result: <span lang="zh-Hans"><strong>重要提示（Important Notice）：</strong>请注意。</span>

## Supported Punctuation

The plugin handles all common ideographic punctuation marks:

- Parentheses: `（）`
- Brackets: `【】「」〈〉`
- Periods: `。．`
- Commas: `，、`
- Questions: `？`
- Exclamations: `！`
- Colons: `：`

## Why This Matters for AI

Language models generate markdown naturally, often placing emphasis markers around phrases that include punctuation. Without CJK-friendly parsing, AI-generated content in Chinese, Japanese, or Korean would have broken formatting.

<dl>
  <dt>❌ Without CJK support:</dt>
  <dd>
    - The model writes:{" "}
    <span lang="ja">`**この用語（読み方など）**について説明します。`</span>- The
    user sees: <span lang="ja">
      \*\*この用語（読み方など）\*\*について説明します。
    </span> (not bold!)
  </dd>
  <dt>✅ With CJK support:</dt>
  <dd>
    - The model writes:{" "}
    <span lang="ja">`**この用語（読み方など）**について説明します。`</span>- The
    user sees: <span lang="ja">
      <strong>この用語（読み方など）</strong>について説明します。
    </span> (properly bolded!)
  </dd>
</dl>

## Configuration

CJK support is enabled by default with no configuration required. The plugins are included in the default remark plugin list:

```tsx
import { Streamdown } from "streamdown";

export default function Page() {
  return <Streamdown>{markdown}</Streamdown>;
}
```

### Disabling CJK Support

If you need to disable CJK support, you can override the default remark plugins:

```tsx
import { Streamdown } from "streamdown";
import remarkGfm from "remark-gfm";
import remarkMath from "remark-math";

export default function Page() {
  return (
    <Streamdown remarkPlugins={[remarkGfm, remarkMath]}>{markdown}</Streamdown>
  );
}
```

Note: This removes all default remark plugins, so you'll need to add back any others you need.