Regex Tester

Test one JavaScript regular expression against sample text in a worker that stops after 400 milliseconds. Nested repeating groups and unknown flags are refused before they run.

Example: Words starting with cat

catch the catalog and a cat

\bcat\w*

A common error

A group that repeats and itself contains * or +, or a flag this engine does not know, is rejected. The page does not return a partial match for that pattern.

The editor runs in the browser after this page loads. Nothing you paste is uploaded unless you save a Pro project.