What is a Regex Tester?
Regular expressions fail silently — a pattern that looks right matches nothing, or too much. Testing live against real sample text is the only sane way to write them.
This tester runs your browser’s actual JavaScript regex engine (the semantics your frontend and Node code will use), showing every match with its position and capture groups as you type.
How to use the Regex Tester
- Type the pattern (without slashes) and flags.
- Paste the test text.
- Read matches, indices and groups in the live table.
Frequently asked questions
Which regex flavor is this?
JavaScript (ECMAScript) — what runs in browsers and Node. Python/Go/PCRE differ in details like lookbehind and named groups.
What do the flags mean?
g = all matches, i = ignore case, m = ^ and $ per line, s = dot matches newline, u = unicode.
Why is my pattern matching empty strings?
Patterns where everything is optional (like a*) match at every position. Anchor them or make part mandatory.
Is my text sent anywhere?
No — matching runs locally.