Regex Tester
Test and debug regular expressions in real-time. See matches highlighted instantly, view captured groups, and explore common regex patterns.
Common Patterns
Match Details
No matches found. Enter a pattern and test string above.
Regex Explanation
Enter a regex pattern to see its explanation.
Features
Real-Time Matching
See matches highlighted instantly as you type your pattern and test string.
Captured Groups
View numbered and named capture groups for every match with index positions.
Flag Toggles
Toggle g, i, m, s, u, y flags with a single click to modify matching behavior.
Pattern Library
Click to load common patterns like email, URL, phone, IP address, and more.
Regex Explanation
Get a breakdown of what each part of your regex pattern does.
100% Client-Side
Everything runs in your browser. No data is sent to any server.
Free Online Regex Tester — Debug Regular Expressions Instantly
Regular expressions are one of the most powerful tools in a developer's toolkit, but writing and debugging them can be frustrating without the right feedback. Our free Regex Tester gives you instant visual feedback as you type, highlighting every match in your test string and showing detailed information about captured groups, named groups, and match positions. Whether you are validating user input, parsing log files, or extracting data from text, this tool makes it easy to get your regex right the first time.
The built-in pattern library includes commonly used regular expressions for email addresses, URLs, phone numbers, IP addresses, dates, and more. Just click a pattern to load it and start testing immediately. The regex explanation panel breaks down each token in your pattern so you can understand exactly what it does — perfect for learning regex or deciphering complex expressions written by others.
All processing happens entirely in your browser using JavaScript's native RegExp engine. Your test strings and patterns are never uploaded to a server, making this tool safe for sensitive data. The tester supports all standard JavaScript regex flags including global matching, case-insensitive mode, multiline, dotAll, Unicode, and sticky.
Frequently Asked Questions
What is a regex tester?▾
A regex tester is a tool that lets you write regular expression patterns and test them against sample text in real-time. It highlights matches, shows captured groups, and helps you debug patterns before using them in code.
Is my data safe when using this regex tester?▾
Yes. All regex matching runs entirely in your browser using JavaScript's native RegExp engine. Your patterns and test strings are never sent to any server.
What regex flags are supported?▾
All standard JavaScript regex flags are supported: g (global), i (case-insensitive), m (multiline), s (dotAll), u (Unicode), and y (sticky). Click the flag buttons to toggle them on or off.
Can I use named capture groups?▾
Yes. JavaScript supports named capture groups using the (?<name>...) syntax. Named groups appear in the match details panel alongside numbered groups.
What regex engine does this tool use?▾
This tool uses the browser's built-in JavaScript RegExp engine. This means it supports ECMAScript regex syntax, which covers most common use cases for web development.
Want to learn more about regex?
Check out our guides on regex basics, common patterns, and flag usage.
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