Regex Tester

Test regular expressions against text with live match highlighting.

Runs entirely in your browser. Your data is never uploaded.

About Regex Tester

Regex Tester runs your regular expression against sample text and highlights every match in real time, with flag toggles and a live match count. It uses JavaScript's native RegExp engine, all in your browser.

Regex Tester is one of dozens of free developer tools on Crystal Toolkit. When you open this page, the tool loads in your browser and is ready to use immediately — there is nothing to install and no account to create. Everything you enter is handled locally using fast, modern web technology, so the work happens on your device rather than on a remote server. This approach keeps your information private, removes upload and download waiting time, and lets the tool keep working even on a slow connection once the page has loaded.

How to use Regex Tester

1Enter a pattern and flags.
2Paste your test text.
3Review the highlighted matches and count.

Key features

Runs in the browser using native, well-tested web APIs
Handles large payloads without sending your data to a server
Gives clear, actionable error messages when input is malformed
100% free with no sign-up, account or watermark
Mobile-first design that works on any device

Common use cases

Debugging API responses and configuration files
Preparing and inspecting tokens, hashes and encoded data
Quickly validating data while building and testing software

Why use Crystal Toolkit?

Unlike many online developer tools, Crystal Toolkit runs Regex Tester entirely inside your browser. That means your data is processed on your own device and is never uploaded to a server, so it stays private and the results appear instantly. There is no sign-up, no daily limit and no watermark — just a fast, focused regex tester you can use as often as you like, on desktop or mobile. Crystal Toolkit is built and maintained by CrystalSoftonic and is funded by unobtrusive ads, which is how we keep every tool completely free.