Regex Tester
A powerful developer tool for building and testing regex patterns with instant match highlighting, capture group inspection, and replace mode.
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How it works
- Browser-first where supported
- No sign-up required for basic use
- Uploads should be auto-deleted after processing once server-side tools are enabled.
Trust and privacy
Free online regex tester that validates and debugs regular expressions with real-time matching — no signup, no data sent to server, works in your browser.
Frequently asked questions
Is Regex Tester really free?
Yes, completely free with no signup, no limits, and no data sent to any server.
Is it safe to test regex with sensitive data?
Yes. All regex testing happens entirely in your browser using the built-in JavaScript RegExp engine. No data is ever transmitted to a server.
Which regex engine does this use?
It uses the browser's built-in JavaScript RegExp engine, which supports ES2024 features including the dotall (s) and unicode (u) flags.
What's the best free regex tester online?
AllUtil's Regex Tester provides real-time match highlighting, capture group inspection, and find-and-replace mode — all free in your browser with no signup required.
Can I use capture groups and replacements?
Yes. Toggle Replace Mode to use $1, $2, and other backreferences for find-and-replace workflows.
Why is this the best free regex tester?
This regex tester provides real-time match highlighting, capture group inspection, and find-and-replace mode using the browser's native JavaScript RegExp engine. It is the fastest way to build, test, and debug regular expressions without leaving your browser.
Key Features
- Real-time match highlighting as you type
- Capture group display with numbered backreferences
- Replace mode with $1, $2 backreference support
- All JavaScript regex flags: g, i, m, s, u, y
- Match count and execution time display
- Common regex pattern library for quick reference
- Shareable regex patterns via URL parameters
Common Use Cases
- Test regex patterns for form validation
- Debug complex regular expressions for data parsing
- Build search-and-replace patterns for text processing
- Learn regex syntax with instant visual feedback
- Validate email, URL, and phone number patterns
- Extract data patterns from log files and CSV data
How It Compares
Many regex testers use server-side engines that differ from JavaScript, leading to unexpected behavior in production. This tool uses the browser's native RegExp engine, ensuring your patterns work exactly as they will in JavaScript applications.
Privacy & Security
All regex processing happens in your browser. Your test strings and patterns are never sent to any server.
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