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Security

Regex Tester

Test a pattern against a string with flags, groups, and a ReDoS timeout guard.

About Regex Tester

Test regular expressions online safely. See matches and capture groups with length/timeout guards — free regex tester on Fah Swe Tools.

How it works

  1. Enter pattern and test string.
  2. Toggle i / m / s flags.
  3. Inspect matches and capture groups.

FAQ

ReDoS?

We enforce pattern/subject length limits and a short match timeout.