Regex Tester
Test a pattern against your own text with live match highlighting. Runs entirely in your browser. Nothing you type is ever uploaded.
What can you do?
RegexCheck tests a regular expression against a block of text you provide, highlights every match inline, and lists each match with its capture groups, updating live as you edit the pattern, flags, or text.
Curious how regex went from math theory to grep? Read Regular Expressions Predate the Personal Computer.
How it works
Every match runs directly in your browser using JavaScript's native RegExp engine. Nothing is sent to a server, so it works even offline once the page has loaded.
Frequently asked questions
Is this free to use?
Yes. There's no sign-up and no limit on how many patterns you test.
Do you store what I type?
No. Matching happens entirely client-side in your browser. See the privacy policy for details.
Which regex flavor does this use?
JavaScript's native RegExp engine. The same one that runs in every browser and in Node.js. Syntax is very close to PCRE, but a few features (like some lookbehind and Unicode property escapes) depend on browser support for the flags you select.
What do the flag checkboxes do?
g (global) finds all matches instead of stopping at the first. i (case-insensitive) ignores letter case. m (multiline) makes ^ and $ match the start/end of each line instead of the whole string. s (dotAll) makes . match newlines too.