Regex Tester — Free Online Tool

How to use the Regex Tester

Test JavaScript regular expressions against sample text, inspect match positions and capture groups, and limit expensive patterns with a separate time-limited worker.

1. Enter the expression without leading or trailing slash delimiters.
2. Choose valid JavaScript flags, for example g for global and i for case-insensitive.
3. Paste sample text and select Test to view matched text, starting indexes and capture groups.
4. Simplify a pattern if the safety timeout is reached.

Accuracy note: Tested input is processed locally in a worker; up to 100 matches are displayed. Browser support for some newer flags varies.

Regex Tester formula and method

JavaScript regular expressions describe patterns to match within strings. For global patterns, exec() iterates over matches; optional capture groups appear after the full match. Flags affect matching behavior.

All numeric results depend on entered measurements, dimensions and settings. Intermediate calculations retain decimal precision; displayed results may be rounded. Verify material specifications, relevant laws and seller fee conditions where applicable.

Worked example

Pattern \b\d{3}-\d{3}-\d{4}\b with flag g can find formatted phone-like numbers such as 555-123-4567. This is a pattern illustration, not phone-number validation.

Adjust the values in the interactive tool above to reproduce this example or model your own situation.

Frequently asked questions