Free Regular Expression Tester
Type a pattern and test text — matches highlight live, with capture groups listed below. JavaScript regex syntax.
Frequently Asked Questions
Which regex flavor does this tester use?
JavaScript (ECMAScript) regular expressions — the same engine your browser uses. Most patterns are portable, but some features differ from other flavors: JavaScript uses (?<name>...) for named groups and does not support possessive quantifiers or atomic groups found in PCRE.
What do the g, i, m, and s flags mean?
g finds all matches instead of stopping at the first. i ignores letter case. m makes ^ and $ match at the start and end of each line rather than the whole text. s lets the dot (.) match newline characters.
Why does my pattern freeze the page on large text?
Patterns with nested quantifiers like (a+)+ can trigger catastrophic backtracking, where the engine tries an exponential number of combinations. Rewrite the pattern to avoid overlapping quantifiers, or anchor it more precisely.
Is my test data uploaded?
No. Matching runs entirely in your browser using its native regex engine. Your patterns and text never leave your device.