Regex Tester
Test regular expressions with live match highlighting and capture group details, with input limits for safety.
Highlighted preview (3)
Hello, Yunedia Tools 2026!
| # | Index | Match | Groups |
|---|---|---|---|
| 1 | 0 | Hello | — |
| 2 | 7 | Yunedia | — |
| 3 | 15 | Tools | — |
How to use
Set a pattern and flags (g / i / m / s / u / y), type the test text, and the results update as you type. Matches are highlighted in the preview, and the table lists each match's index, text and capture groups (including named groups). Without the g flag, only the first match is reported, matching JavaScript semantics.
Notes
Evaluation uses your browser's JavaScript regex engine, locally. To limit freezes from catastrophic backtracking, the pattern is capped at 500 characters, the test text at 20,000 characters and matches at 1,000. Even within those caps, patterns with nested quantifiers can be slow — simplify the pattern if the page stalls.
FAQ
Is this the same regex flavor as other languages?
This is JavaScript's flavor. The basics are shared, but details differ from PCRE or Python: \d matches ASCII digits only, and named groups use the (?<name>...) syntax.
What happens with patterns that match empty strings?
The search position advances by one character after an empty match to avoid an infinite loop, and empty matches appear as zero-width markers in the preview.