Regex Tester

100% private. Your pattern and test text run entirely in your browser — nothing is uploaded, stored, or sent anywhere.

Developer / Code

Test a regular expression

JavaScript regex flavor. Matches are always listed globally, with each match's position and capture groups.

Pattern (without slashes) Flags i — case-insensitive m — multiline (^ and $ match line starts) s — dotAll (. matches newlines) u — Unicode Test text

Matches

Enter a pattern and test text to see matches.

When NOT to use Regex Tester

A pattern that works here may still behave differently in Python, Java, or PCRE — check flavor-specific features (like \K or possessive quantifiers) before porting.
Catastrophic patterns (nested quantifiers on long input) can hang any regex engine — if the page stalls, shorten the test text and simplify the pattern.

Questions people ask

Is my input sent to a server?

No. This tool runs entirely in your browser using JavaScript. Nothing you paste is uploaded, stored, or sent anywhere.

Which regex flavor is this?

JavaScript regular expressions — the same syntax used in browsers and Node.js. Most patterns transfer to other languages, but lookbehind, named groups, and flag support differ by flavor.

How are matches listed?

Every match is listed in order with its index in the text and any capture groups it contains. Matching is always global here so you can see all results at once.