Regular expression tester
Experiment with patterns against sample text before using them in code.
How it works
The tool uses the browser JavaScript RegExp engine and lists every global match with its character index.
Technical limitation
Regular-expression syntax and behavior can differ between programming languages.
Privacy
Input stays in this browser and is not intentionally uploaded.
A practical guide to Regular expression tester
Test a JavaScript regular expression, flags, match text, and indexes. This page handles one focused task so you can reach a result without creating an account. The core operation runs in the current browser unless an external resource is clearly identified.
How to get a reliable result
- Begin with a clean source value or file and confirm that every selected unit and option matches your goal.
- Run the tool, then compare the result with the original requirement instead of relying only on a success message.
- Copy or download the output and test it in the destination where it will actually be used.
Limitations and good practice
Browser tools reduce repetitive work, but the final output still needs human review. Keep an untouched copy of important source material. Browser support, rounding, source quality, encoding, and platform rules can affect results.
Frequently asked questions
Is this tool free?
Yes. No account or credits are required. Normal internet data charges may still apply.
Does the site retain my input?
The core task runs in the browser and the site does not intentionally retain the submitted value or selected file. External libraries and links have their own policies.
Should I verify the output?
Yes. Review calculations, code, files, and images before using them for financial, legal, accessibility, security, or production decisions.