JavaScript regular expressions as in your browser—useful for front-end validation patterns and docs examples.

Very chatty patterns on long inputs could freeze the tab; we stop after 500 global matches.

Free toolsRegex tester

Regex tester

Validate patterns for course forms, code samples, and API tutorials—no server round trip.

Pattern

JavaScript RegExp—handy for validating lesson IDs, URLs in docs, or API examples.

Test string

Matches (2)

With the global flag, execution stops after 500 matches to keep the page responsive.

Frequently asked questions

Which regex flavor?: JavaScript regular expressions as in your browser—useful for front-end validation patterns and docs examples.
Why cap matches?: Very chatty patterns on long inputs could freeze the tab; we stop after 500 global matches.