Free Regex Tester and Debugger

What is a regex tester?

A regular expression (regex) is a pattern that describes a set of strings, used for searching, validating, and extracting text. A regex tester lets you write a pattern, run it against sample text, and see exactly what it matches, so you can build and debug the expression before you drop it into your code. It is one of the fastest ways to get a tricky pattern right.

How to use this regex tester

Type your pattern in the Regular expression box and any flags (such as g, i, m, s) in the Flags box, then paste sample text in the Test string box. Matches update as you type: each result shows the matched text, its index, and the value of every capture group. Everything runs in your browser, so nothing you paste is uploaded.

Common flags

• g global, find all matches instead of stopping at the first
• i case-insensitive
• m multiline, so ^ and $ match at line breaks
• s dotall, so . also matches newlines

Regex FAQ

Which regex flavour is this? The JavaScript (ECMAScript) engine, the same one browsers and Node.js use.

Why does my pattern not match? Check that special characters are escaped, that the g flag is set when you expect multiple matches, and that anchors like ^ and $ behave as you intend with the m flag.

Is my data safe? Yes. The tester runs entirely in your browser and never sends your pattern or text anywhere.