Which regex flavor does this use?

It uses JavaScript's native RegExp engine, which supports ECMAScript regular expressions including lookbehinds, named groups, and Unicode properties.

Can I test replace patterns?

Yes. Enter a replacement string and the tool shows a live preview of the substituted result, supporting backreferences like $1, $2.

Absolutely. All regex processing happens locally in your browser. No data is transmitted to any server.

Regex Tester & Matcher

Evaluate exact JS regular expressions, extract capturing groups, and preview global string replacements natively.

Regular Expression

Test String Input

Length: 55 chars6 Matches

Highlighted Match Execution

Hello World, this is a Regex tester. Match These Words!

Capturing Groups (6)

Match 1Index: 0

Full Match

Hello

Group 1

Match 2Index: 6

Full Match

World

Group 1

Match 3Index: 23

Full Match

Regex

Group 1

Match 4Index: 37

Full Match

Match

Group 1

Match 5Index: 43

Full Match

These

Group 1

Match 6Index: 49

Full Match

Words

Group 1

Evaluate Replacement

Replace with:

, this is a tester. !

What is a Regex?

A Regex Tester is a developer tool for writing, testing, and debugging regular expressions interactively. It highlights all matches in your test string in real time, shows captured groups, supports all standard flags (g, i, m, s, u), and provides a replace preview — all without leaving your browser.