Regex

A free online regular-expression tester and debugger that highlights matches live as you type your pattern and test text. It shows a table of every capture group — including named groups — so you can see exactly what each part of your expression matched, and a replacement preview lets you confirm a find-and-replace before you apply it in your editor or code. It uses the JavaScript (ECMAScript) engine and supports all the standard flags, so patterns you validate here behave the same way in your JavaScript and TypeScript projects. Everything runs in your browser, so your patterns and sample data stay private.

Common uses

• Develop and debug a pattern against sample text with instant match highlighting.
• Inspect what each capture group matched, including named groups.
• Preview the result of a find-and-replace before applying it in your code.
• Validate that a pattern behaves correctly across multiple test strings.
• Build and refine a validation regex for emails, URLs, or IDs.

Frequently asked questions

Which regex flavor and flags are supported?

It uses the JavaScript (ECMAScript) engine and supports the g, i, m, s, u, and y flags, so results match how the pattern runs in JavaScript and TypeScript.

Can I test replacements?

Yes. Provide a replacement string (with $1,

Does it show named capture groups?

Yes. The capture-group table lists both numbered and named groups so you can verify exactly what each part of the pattern captured.

Are my pattern and test text sent anywhere?

No. Matching runs entirely in your browser, so your regular expression and sample data never leave your device.

Why does my pattern behave differently than in another language?

This tester uses the JavaScript regex engine. Other flavors (PCRE, Python, .NET) differ in features like lookbehind and named-group syntax, so a pattern may need adjusting for those environments.