Regex Tester Online
Test JavaScript regular expressions with live matches.
Method and limitations reviewed August 3, 2026. Browser-first, no login required.
Matches
9
Thequickbrownfoxjumpsoverthelazydog
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About this tool
What this tool does
The tester runs a JavaScript regular expression against sample text and lists the matched strings. It provides a small, focused environment for checking a pattern before adding it to application code.
How the result is produced
- Patterns are compiled with the browser's JavaScript RegExp engine.
- The available controls toggle global, case-insensitive and multiline flags.
- Global mode advances through every match and guards against zero-length loops.
- For readability, the visible match list is capped at the first 200 matches.
Good uses
- Checking extraction patterns against representative text
- Comparing case-sensitive and case-insensitive behavior
- Finding syntax mistakes before using a pattern in JavaScript
How to verify the result
- Test positive, negative and empty-input examples.
- Include Unicode, line breaks and unusually long text when your real data contains them.
- Measure performance in the target application before trusting a complex pattern.
Known limitations
- Regex syntax and features can differ between programming languages.
- The tool lists matched text but does not display capture groups or replacement output.
- A pattern that works on a short sample can still backtrack badly on large input.