About

Built for developers.

Regexx is a free, privacy-first regular expression tester that runs entirely in your browser — no sign-up, no server, no nonsense.

The philosophy

Most regex tools phone home. They send your test strings to a server, log your patterns, and ask you to create an account before you can use half the features. We think that's backwards.

Regexx runs on the JavaScript regex engine already built into your browser. Your patterns and test strings stay on your device — always. The Web Worker architecture means even complex regex operations never block the UI.

No tracking. No telemetry. No ads (we're working on that). Just a fast, focused tool that gets out of your way.

What you get

Live Matching

Matches update as you type. Every match highlighted inline with position and capture group data.

Web Worker Engine

Regex runs off the main thread via a Web Worker — no freezing on large inputs or complex patterns.

Find & Replace

Apply replacements with full support for backreferences like $1 and named groups.

Flags Control

Toggle g, i, m, s with one click. Pattern updates instantly.

Quick Snippets

12 ready-made patterns for emails, URLs, dates, UUIDs, and more — one click to load.

Cheat Sheet

Quick reference panel covering character classes, quantifiers, anchors, groups, and flags.

Part of RuntimeHub

Regexx is one of many free, privacy-first tools built by RuntimeZero under the RuntimeHub umbrella. All tools share the same philosophy: browser-native, no login, no data harvesting.

Explore RuntimeHub →