/regex — Regex Lab
Build and understand regular expressions: live match highlighting, capture-group table, replace preview, a plain-English explainer, a pattern library, and pattern-from-samples — all in your browser with the native engine (lookaround, backreferences, named groups).
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Enter a pattern to begin.
Pattern library
Test string
Highlighted
Find & replace
Result
Explain this pattern
The pattern broken down, token by token.
Generate a pattern from samples
Paste example strings, one per line — get a starting pattern to refine.
Cheat sheet
Regex syntax reference — click a token to insert it into the pattern.