Regex Tester

The Regex Tester lets you build and test regular expressions against your own sample text, highlighting matches live as you type and showing capture-group details and the active flags. It uses JavaScript's built-in RegExp engine, supporting most common syntax including character classes, lookaheads and named groups.

Developers use it to craft and debug patterns for input validation, search-and-replace and text parsing without having to run code inside their actual project. Watching matches light up the instant you change the pattern turns regular expressions from intimidating guesswork into a fast, iterative process you can actually reason about.

Everything runs in your browser, so your test strings — which may contain real or representative data — are never uploaded anywhere. With no install and no account, it makes a reliable scratchpad for working out a tricky pattern before you commit it to your codebase. Keeping the work local also means the sample data you use to test a pattern never leaves your browser.