Regex Tester.

See every JavaScript regex match, group, and replacement before it reaches your code.

Runs entirely in your browser

Regular expression

JavaScript syntax. Flags: d g i m s u v y.

Test text

Replacement preview optional

MATCH PREVIEW

Highlighted text

CAPTURES

REPLACE

Ready.

FIELD NOTES / 008

Test the exact JavaScript expression and flags your app will use. Named and numbered capture groups are listed for every match.

Can a regular expression freeze a page?

Pathological patterns can take a long time. This tester evaluates matches in a Web Worker and stops work that exceeds its time limit.

Which regex flavor is this?

JavaScript, as implemented by your browser. Other languages can interpret escapes, flags, and advanced features differently.