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Find CSS that breaks Chinese, Japanese, Korean or Thai text badly: word-break, lang, line height and spacing

CJK line breaking checkFreeFor developers and designers

25/day

free runs a day, no sign-in.

Before: what you give it

The example input, as typed in. You paste text, CSS, markup or notes.

<html><style>p{word-break:break-all;line-height:1.2;max-width:60ch;letter-spacing:.05em;font-style:italic}</style><body><p>これは日本語の文章です。<br>改行が手動で入っています。、閉じ括弧</p><p>한국어 문장입니다 여러 단어로 구성되어 있습니다.</p></body></html>

After: what comes back

The first lines of a real run on that input. Nothing here is edited by hand.

CJK LINE BREAKING CHECK
Characters: Han 26, kana 28, Hangul 42, Thai 0
Findings: 2 high, 1 medium, 4 low, 1 info

[HIGH] CSS Text (convention): word-break: break-all
  Breaks anywhere, which suits dense CJK columns but splits Latin words mid-word and ignores Korean word spaces.
  Seen in: p
  Fix: For Korean use word-break: keep-all. For mixed text prefer overflow-wrap: anywhere or break-word and let normal rules handle CJK.

[HIGH] WCAG 3.1.1 / 3.1.2; HTML lang: CJK text with no lang attribute
  Browsers pick the Han glyph variant and the line-breaking dictionary from lang. A wrong choice shows Japanese forms in Chinese text or the reverse.
  Fix: Set lang="ja", "zh-Hans", "zh-Hant" or "ko" on the page or the element.

[MEDIUM] Line breaking: 1 manual <br> inside CJK text
... full output on the tool page

What you get

Character counts by script and findings on word-break, lang, line-height, letter-spacing and stray breaks

What it cannot do

Static review of pasted source and sample text; it does not render the text.

Who it is for

  • Developers
  • Designers

Free and Pro

Free25 runs a day per IP address, up to 100,000 characters a run.
ProNo daily limit, 300 requests a minute, up to 200,000 characters a run.

What each plan includes

Use it from your assistant

The tool is called check_cjk_line_breaking. Connect the server once, then ask for it by name or just describe the job. Install steps for each app.

claude mcp add --transport http designers https://designers.allthepossibles.com/mcp
curl -X POST https://designers.allthepossibles.com/api/cjk-line-breaking -H 'content-type: application/json' -d '{"source":"<html><style>p{word-break:break-all;line-height:1.2;max-width:60ch;letter-spacing:.05em;font-style:italic}</style><body><p>これは日本語の文章です。<br>改行が手動で入っています。、閉じ括弧</p><p>한국어 문장입니다 여러 단어로 구성되어 있습니다.</p></body></html>"}'

Try it here

The form starts with the same example input, so you can run it first and then swap in your own.

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