Regex Tester: Test & Debug Regular Expressions Online
Test regex, debug patterns, and inspect matches entirely in the browser with zero data uploads.
Test regex patterns, see matches highlighted in real time, and debug regular expressions — all in your browser.
Free online regex tester — test regex patterns against sample text, toggle flags, inspect matches and capture groups in real time. Runs locally in your browser, so your test data stays private.
How this page is maintained
- Steps and copy are checked against the current tool behavior.
- Browser limits, file-size constraints, or compatibility gaps are documented when relevant.
- Unless a page explicitly says otherwise, files and text stay in the browser during processing.
Free Online Regex Tester & Debugger
Test your regular expressions against real text and see matches highlighted instantly. Whether you're validating emails, parsing log files, extracting data from HTML, or debugging a stubborn pattern, this regex tester gives you immediate visual feedback without leaving your browser.
If you searched for a regex checker, test regex online, or a regular expression debugger, this page is built for that exact feedback loop: type the pattern, type the test text, and see the matches immediately.
Real-Time Validation Loop
As you type your pattern, the interface instantly evaluates the payload, highlighting positive matches, extracting capture groups, and visually exposing greedy quantifiers that might unintentionally swallow your entire document. No more guessing—see exactly what your regex matches (and what it misses) on every keystroke.
Built-In Starter Patterns
Not sure where to start? One-click presets cover the most common regex patterns: email addresses, phone numbers, IP addresses, hex color codes, URLs, and dates. Load a starter, then customize it for your specific use case.
Environment Parity with JavaScript
This tool uses your browser's native JavaScript RegExp engine—the same engine running in Node.js, React, Vue, and every major JavaScript framework. The patterns you validate here will behave identically in production. Toggle flags (global, multiline, dotAll, case-insensitive, Unicode, sticky) with one click.
Your Data Stays Private
Unlike cloud-based regex testers, your test strings never leave your device. This matters when you're testing against production logs, user data, API responses, or any text containing sensitive information.
Key features
- Instant highlighting: Matches and capture groups update as you type, so you can iterate without reloading.
- Flag toggles: Switch global, multiline, dotAll, and case-insensitive modes in one tap to mirror production behavior.
- Starter snippets: One-click patterns for emails, phone numbers, IP addresses, hex colors, and invoice IDs jumpstart testing.
Frequently asked questions
How do I test regex online?
Enter your pattern, paste sample text, and toggle flags like g, i, or m. Matches highlight instantly so you can debug the pattern before using it in code.
How do I see all matches?
The tester auto-enables the global flag when highlighting so every match is visible at once.
Which regex engine is used?
We use your browser's native JavaScript RegExp engine. This ensures that the patterns you test here will work exactly the same way in your JS code.
What flags are supported?
We support standard flags: Global (g), Case Insensitive (i), Multiline (m), DotAll (s), Unicode (u), and Sticky (y).
Is my text stored?
No. Everything runs client-side. Closing the tab clears your inputs.
Can it handle Unicode?
Yes. Enable the “u” flag to work with emoji, accented characters, and non-Latin scripts.
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