Turn text into
something useful.
Find, extract, validate and transform. Learn regular expressions through real experiments, visible matches and a growing collection of small wins.
12 guided lessons · 8 challenges · Real JavaScript regexTry a pattern. See exactly what it finds.
Browser-local • no text uploadsRegex runs in an isolated worker with a 1.5-second timeout. Results show up to 300 matches. Zero-length matches appear as ◆. Indices use UTF-16 code units.
Quick reference
\d digit · \s whitespace · [abc] character choice · + one or more · * zero or more · ? optional · {2,4} repetition range · (...) capture · | alternative
Flags and syntax here follow your browser's JavaScript engine. Other languages may differ.
Your match inspector
Run your pattern to begin.
Match positions and captures
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Replacement preview
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Reusable JavaScript
Small steps, stronger patterns.
Make the examples pass.
Write a pattern that accepts every positive example and rejects every negative example. Tests use fresh regex instances, so the global flag does not carry state between cases. Passing means these cases pass, not that the pattern is universally correct.