About Regex Tester Online Free — Regular Expression Debugger
Test complex pattern-matching algorithms, validate form inputs, and debug capture groups with instant visual feedback and complete confidentiality.
Key Features & Capabilities
- Real-time visual regex match and capture group highlighting
- Support for all standard flags (g, i, m, s, u, y)
- Detailed match breakdown with string indexes and groups
- Built-in regular expression cheat sheet and templates
- 100% private in-browser regex engine
How to Test Regular Expressions Online
Step 1: Enter Regex Pattern
Type your regular expression pattern and choose active flags.
Step 2: Input Test String
Paste the sample text you want to match against.
Step 3: Inspect Matches
View highlighted matching substrings and extracted capture groups in real-time.
Frequently Asked Questions
Which regex dialect does this tester use?
It runs the standard ECMAScript / JavaScript regular expression engine built natively into your browser.
Are common patterns like emails and URLs included in templates?
Yes! Our cheat sheet includes ready-to-use patterns for emails, phone numbers, URLs, dates, and IP addresses.
Related Utility Tools
Why Zaeyon?
Private, free, and browser-based — no account, no uploads, no compromises.
Zero Uploads
Your files never leave your device. All processing happens locally in your browser memory — nothing is sent to any server.
100% Free Forever
No subscriptions, no hidden fees, no daily limits. Every tool on Zaeyon is permanently free to use without an account.
Instant & Powerful
Powered by WebAssembly — the same low-level technology used in native apps — so processing is fast even for large files.
Works Offline
Once the page loads, the WebAssembly engine runs entirely on your device. No internet connection needed to process files.
Works Everywhere
No software installation required. Runs directly in your browser on Windows, Mac, Linux, iOS, and Android.