Regular Expression Tester

Test a regular expression pattern against a text, with flags, matches, named groups, indices, and a replace mode. The expression always runs inside a dedicated Web Worker, never on the main thread, with a configurable timeout: if it's exceeded, the Worker is terminated and TIMEOUT is shown without automatically running again. It includes heuristic warnings about patterns at risk of catastrophic backtracking, without claiming to detect every ReDoS vulnerability.

Processed on your device, no AIpatrón hasta 500 caracteres, texto hasta 200.000 caracteres, timeout configurable

The data is processed on your device and is never sent to the server.

Use cases

Test a validation pattern before using it in code
Extract data from a text with named groups
Try out a replacement before applying it to a real file

How to use this tool

Type the pattern, flags, and test text
Review the matches, groups, or replacement result
Copy the pattern or the result

Frequently asked questions

Does it detect every expression vulnerable to ReDoS?

No. It shows heuristic warnings about patterns with typical risk shapes (nested quantifiers, overlapping alternations), but it can't guarantee it detects every possible vulnerability.

What happens if my pattern takes too long?

The Web Worker running it is terminated and TIMEOUT is shown; the tool doesn't automatically re-run the same pattern.

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