Regex Tester
Test and debug regular expressions with real-time matching and highlighting.
Common flags: g (global), i (case-insensitive), m (multiline), s (dotAll), u (unicode), y (sticky)
About Regex Testing
This tool helps you test and debug regular expressions in real-time. Enter a regex pattern, add flags if needed, and see matches highlighted in your test text. Perfect for developers working with text processing and validation.
About this Regex Tester
Test and debug regular expressions with real-time matching and highlighting. Enter a regex pattern and sample text to see which parts match, capture groups, and any syntax errors. Essential for developers and anyone learning or using regex in code, configs, or search. The tool uses JavaScript's RegExp (ECMAScript) flavor, so patterns are compatible with JS, Node, and many other environments. All processing runs in your browser—your patterns and text never leave your device. Use it to validate patterns before deploying, learn how regex works, or extract and verify data-matching logic.
Key Features
Real-time match highlighting so you see exactly what the pattern matches
Capture groups displayed so you can verify (group1), (?:non-capture), etc.
Clear error messages when the pattern has syntax errors
Sample text area to paste or type test strings
Support for flags: global (g), case-insensitive (i), multiline (m)
Runs in your browser; no server uploads
How to Use
Enter your regular expression in the pattern field
Add flags (g, i, m) if you need global, case-insensitive, or multiline matching
Enter or paste sample text in the test area
View matches and capture groups in the output
If the pattern is invalid, read the error message and fix the syntax, then retest
Popular Use Cases
Debug regex: quickly see why a pattern does or does not match
Validate patterns before adding them to code or configs
Learn regex: experiment with ., *, +, ?, [], (), and character classes
Extract data patterns: test that your regex captures the right parts of a string
Tips & Best Practices
Use flags as needed: g for all matches, i for ignore case, m for ^ and $ per line. Escape special characters (e.g. \. for a literal dot, \( for parenthesis).
In character classes [], many symbols lose special meaning—but - and ] may need escaping.
Test with edge cases: empty string, long text, and strings with special characters.
Frequently Asked Questions
What regex flavor is used?
JavaScript's RegExp (ECMAScript). Supports standard syntax: ., *, +, ?, [], (), |, \d, \w, \s, anchors ^ and $, and common modifiers.
Why is my regex not matching?
Check escaping: . matches any character; \. matches a literal dot. Use the g flag if you expect multiple matches. Ensure character classes and quantifiers are correct.
Can I test capture groups?
Yes. Use parentheses in your pattern (e.g., (\d+)) and the tool will show matched groups so you can verify extraction.
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