Regex Tester - Test Regular Expressions Online
Build, test, and debug your Regular Expressions instantly. Our Free Regex Tester highlights matches in real-time as you type, all processed locally for ultimate privacy and speed.
What is the Regex Tester?
A Regex Tester is an interactive developer sandbox used to write and evaluate Regular Expressions (regex). Writing regex can be incredibly confusing, as one misplaced character can break the entire pattern. This tool allows you to input your test string and your regex pattern side-by-side. As you type, the tool instantly highlights exactly what your pattern is matching, helping you debug greedy quantifiers or faulty lookaheads. It utilizes your browser's native JavaScript regex engine, ensuring your test data is never sent over the internet.
Why Use Our Regex Tester?
- Real-Time Feedback: See exact matches highlighted instantly as you type.
- Flag Support: Easily toggle global (g), case-insensitive (i), and multiline (m) flags.
- Total Privacy: Test sensitive data like emails or logs without uploading anything.
- Client-Side Speed: Zero latency because it runs directly on your device.
How to Use the Regex Tester
Enter the text you want to search through in the 'Test String' area.
Type your regular expression pattern in the top input box.
Toggle your desired regex flags (e.g., Global, Case Insensitive).
Watch the matches highlight instantly in the test string area.
Frequently Asked Questions
It uses the native JavaScript (ECMAScript) regular expression engine built into your web browser.
Yes. Because the tool runs entirely client-side, your log files and proprietary strings are never transmitted to our servers.
Yes, standard JavaScript capturing groups and lookarounds are fully supported and evaluated in real-time.
All file processing is performed locally in your web browser. We do not upload, store, or view your data.