What Regex Tester does
Regular expressions are easier to debug when every match, capture group, and replacement can be inspected against realistic text. This workspace uses the browser JavaScript regular-expression engine and never uploads the pattern or test data.
Common uses
- Highlight and count matches before changing code
- Inspect numbered and named capture groups
- Preview replacements without modifying the original text
Privacy and limitations
The pattern, flags, source text, and replacement remain in this browser tab. Results follow JavaScript regular-expression semantics.
Validate important output in the actual language, database, or target platform.
Frequently asked questions
Which regex flavor is supported?
The tool uses the JavaScript RegExp engine available in your browser, including supported named groups, lookarounds, and Unicode flags.
Why does the result differ from Java or PCRE?
Regex syntax and escaping rules vary between engines. Verify the final expression in the language or platform where it will run.
Can zero-length matches freeze the page?
The matcher advances after an empty match and limits the number of displayed matches to keep the page responsive.