正規表現テスター

What is Regex Tester?

Regular expressions (regex) are powerful pattern-matching sequences used in text processing, input validation, search-and-replace, and data extraction. Regex syntax can be difficult to debug without visual feedback. DailyDevTools' Regex Tester highlights all matches in real-time as you type, shows capture groups, supports all JavaScript regex flags (g, i, m, s, u), and explains what each part of your pattern does in plain English.

How to use Regex Tester

1. 1Enter your regex pattern in the Pattern field (without wrapping slashes)
2. 2Select the flags you need: g for global, i for case-insensitive, m for multiline
3. 3Paste your test string in the Test area — all matches are highlighted instantly
4. 4Review the Matches panel to see each match, its index, and any named capture groups

Frequently asked questions