🔍 Regex Tester
Test JavaScript regular expressions against any string, toggle the g/i/m/s flags, and see every match with its index and capture groups — with a friendly error for invalid patterns, all in your browser.
🧪 Match, Group & Debug
What is a Regex Tester?
A regex tester compiles your pattern and runs it against sample text so you can see exactly what it matches before you ship it. It surfaces each match, its position in the string, and any capture groups, and reports invalid patterns clearly instead of failing silently.
Use AskMeCode's tester to build and debug patterns for validation, search-and-replace, log parsing, and data extraction — iterating on your test string until the matches are precisely what you intend.
❓ Frequently Asked Questions
Which regex flavor does this use?
It uses JavaScript's built-in RegExp engine, the same one that runs in Node.js and every modern browser. Patterns you validate here behave identically wherever you paste them into your JavaScript or TypeScript code, so there are no surprises later.
What do the g, i, m, and s flags do?
g (global) finds every match instead of stopping at the first one; i (ignore case) makes the pattern case-insensitive; m (multiline) lets ^ and $ match at line breaks instead of only the start and end of the whole string; and s (dotAll) lets . match newline characters too.
How are capture groups shown?
Each match lists its full matched text, its index in the input string, and the contents of every capture group in order. That makes it easy to confirm your parentheses are grabbing exactly the sub-strings you expect before relying on the pattern in real code.
What happens if my pattern is invalid?
Instead of crashing, the tool catches the error and shows the engine's message — for example an unterminated group or an invalid quantifier — so you can fix it and try again. Everything runs locally in your browser, so nothing you type or paste is uploaded anywhere.