Regex Tester & Visualizer Online
Test regular expressions directly in your browser with instant highlighting, syntax feedback, flags, and visual capture-group inspection. Your test text stays local on this page.
Result
0 matchesHow to use the Regex tester
Enter an expression, choose the flags, paste sample text, and run the tester. Matching text is highlighted immediately. If the expression contains a syntax error, RegexArena displays the error without breaking the page.
Test both successful and unsuccessful examples. A pattern that matches one example is not necessarily correct for the full requirement.
Visualize capture groups
The RegexArena Regex X-Ray helps explain patterns with capture groups and named groups. Instead of seeing only “match” or “no match,” you can inspect which part of the text each group captured—useful when a pattern almost works but captures the wrong section.
Lookahead and lookbehind are zero-width assertions, so they check context without consuming it. The visual feedback helps distinguish the text that was captured from the context that only had to be present.
Regex examples to test
| Goal | Pattern |
|---|---|
| Numbers only | ^\d+$ |
| Extract integers | \d+ |
| Simple email shape | ^[\w.-]+@[\w.-]+\.[A-Za-z]{2,}$ |
| DEV-0000 code | ^DEV-\d{4}$ |
| Repeated whitespace | \s+ |
Regex tester vs Regex generator
A tester checks and explains a pattern you control. A generator tries to create a pattern from examples or a description. RegexArena currently focuses on testing, visualization, and learning so you can understand the expression instead of receiving an opaque generated pattern.
Practice after testing
When a pattern works in the tester, try rebuilding it from a requirement instead of copying it. That is the skill the 24-level game and the exercise library are designed to train.