Regex Tester
Test and debug regular expressions in real-time. See matches highlighted instantly with support for all JavaScript regex flags.
Features
- ✓Real-time regex matching with instant feedback
- ✓Support for all JavaScript regex flags (g, i, m, s, u)
- ✓Highlighted matches in the test string
- ✓Display of capture groups and named groups
- ✓Match count and position information
- ✓Works offline - no data sent to servers
How to Use
- 1Enter your regular expression pattern in the pattern field
- 2Select the flags you want to use (global, case-insensitive, etc.)
- 3Type or paste your test string in the input area
- 4View highlighted matches and capture groups instantly
- 5Adjust your pattern until you get the desired matches
Examples
Input
Pattern: [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}
Test: Contact us at support@example.com or sales@company.orgOutput
Matches: support@example.com, sales@company.org
Input
Pattern: \d+ Test: Order #12345 contains 3 items totaling $99.99
Output
Matches: 12345, 3, 99, 99
Input
Pattern: (?<year>\d{4})-(?<month>\d{2})-(?<day>\d{2})
Test: Date: 2024-03-15Output
Match: 2024-03-15 Groups: year=2024, month=03, day=15
What is a Regex Tester?
Regular expressions (regex or regexp) are powerful patterns used to match, search, and manipulate text. They form a specialized language for describing character patterns and are supported in virtually every programming language, text editor, and command-line tool. A regex tester helps you write and debug these patterns interactively.
Writing regex can be tricky because the syntax is compact and cryptic. A regex tester provides immediate visual feedback, showing you exactly what your pattern matches in real-time. This makes it much easier to develop complex patterns incrementally, testing each part as you build it up.
Our regex tester uses JavaScript's RegExp engine, which supports modern features like named capture groups, lookahead, lookbehind, and Unicode character classes. The flags panel lets you toggle options like global matching (g), case-insensitive (i), multiline mode (m), and dotAll mode (s).
The tool highlights all matches directly in your test string, so you can see exactly where matches occur. It also shows detailed information about each match, including its position, length, and any captured groups. This is invaluable for debugging patterns that aren't matching as expected.
All processing happens locally in your browser using JavaScript. Your regex patterns and test data are never sent to any server. This makes the tool completely private and safe to use with sensitive data, and it works even when you're offline.