01
Enter a pattern
Paste the expression without slash delimiters, then select only the flags you intend to use.
Developer Tools
Regex Tester
Test a regular expression against sample text locally, with visible flags, matches, capture groups, and a time limit.
0 / 500 pattern characters
0 / 100,000 sample-text characters
Data handling
Storage and export controls
- Retention
- The tool's working state is kept only while this page is open. Inputs and results are not saved to persistent storage by Got A Tool.
- Export
- The tool may prepare a result after you run it. It downloads or copies it only when you choose that action.
Advertising and analytics are separate site services. We do not send selected tool input to them. Read the Privacy Policy for details.
How it works
Test pattern behavior without sending sample text away
02
Use representative text
Add sample input that includes expected matches and a nearby non-match.
03
Review captures
Check each matching value, its starting index, and any capture groups before using the pattern elsewhere.
Clear limit
A timeout is a stop, not a verdict.
The expression runs away from the main page interface and is stopped after one second. A timeout means the test did not finish within that limit. It does not prove that the pattern is invalid or safe for every possible input.
Local worker
Pattern and sample text remain in the browser.
Visible flags
The selected JavaScript flags are always shown.
Capture groups
Each reported match lists numbered capture values.
Bounded results
The page shows at most 500 matches for a readable review.
FAQ
Common questions
Should I include slash characters around my expression?
No. Enter the pattern only, then choose flags from the visible controls.
Why did my test stop after one second?
Some patterns have expensive behavior on particular text. The worker was terminated to keep the page responsive.
Does this test another regex engine?
No. It uses the browser's JavaScript regular-expression behavior. Other languages and tools may interpret expressions differently.
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