Regex Tester
Live regular expression tester with match highlighting, group capture, and flag controls.
Frequently Asked Questions
What are regex flags? +
Flags modify how the regex engine searches. g finds all matches instead of just the first. i makes matching case-insensitive. m makes ^ and $ match the start/end of each line rather than the whole string.
What are capture groups? +
Capture groups are defined with parentheses (). They let you extract specific sub-parts of a match. For example, (w+)s(w+) captures two words separately from a two-word match.
Why does my regex not match? +
Common reasons: missing the g flag when expecting multiple matches, incorrect escaping of special characters, or case mismatch without the i flag. Check the error message shown if the pattern is invalid.
Is my data sent to a server? +
No. All regex testing runs entirely in your browser using JavaScript's built-in RegExp engine. Nothing is transmitted to any server.
How to Use
- 1
Enter your pattern
Type your regular expression in the pattern field. Select flags (g, i, m, s) as needed.
- 2
Enter test text
Paste the text you want to test against. Matches are highlighted in real-time as you type.
- 3
Review matches and groups
See all matches listed below with their positions and any named or numbered capture group values.
Frequently Asked Questions
- JavaScript regular expressions (ECMAScript). This covers the vast majority of regex syntax including lookaheads, backreferences, and named capture groups.