Regex Tester は何をしますか？
Regex Tester はブラウザ上でデータを調査するツールで、結果と制限を明確に示します。 検証済みの機能： JavaScript RegExp engine, Capture groups, 300 ms worker timeout, 1,000-match cap.
Test against the deployment engine
Use this page for JavaScript patterns. Verify a PCRE, Python, .NET, Java, database, or proxy pattern in that exact engine before deployment.
使い方
- Enter the pattern without surrounding slash characters.
- Choose JavaScript flags and paste representative test text.
- Inspect highlighted matches, indexes, and capture groups.
実際の入出力例
Capture a named numeric identifier
入力
Pattern: order-(?<id>\d+)
Text: order-1042出力
Match: order-1042
Named group id: 1042The browser exposes the full match and the named capture from the JavaScript RegExp result.
一般的なエラーと対処
| 症状 | 原因 | 対処 |
|---|---|---|
| A valid-looking pattern is rejected. | It uses syntax from another regex engine or an unsupported browser flag. | Rewrite the expression for the target JavaScript runtime. |
| Testing times out. | The expression backtracks heavily on the supplied text. | Make repetitions more specific, reduce ambiguity, or use a parser. |
A timeout indicates expensive matching
このツール固有の制限： Nested quantifiers and ambiguous repeated groups can cause excessive backtracking. A 300 ms timeout protects the page but does not certify production safety.
標準と実装の参考資料
- MDN — RegExp (opens in a new tab)Documents JavaScript pattern syntax, flags, and match behavior.
Regex Tester — FAQ
Which regex engine is used?
The page uses JavaScript RegExp; PCRE, Python, .NET, and Java can behave differently.
Are capture groups shown?
Yes. Numbered captures and named groups are shown for displayed matches.
What does the timeout mean?
The worker is stopped after 300 ms to reduce page freezes; this is not proof that a pattern is safe.
更新内容
実質的な更新： Regex Tester: Added JavaScript flag validation, highlighted matches, capture groups, a 1,000-match cap, and 300 ms worker termination for slow patterns.