What do \d, \w, and \s mean?

\d matches a digit, \w a word character (letters, digits, underscore), and \s whitespace. Uppercase versions (\D, \W, \S) match the opposite.

What is the difference between * and +?

* matches zero or more of the preceding token; + matches one or more; ? matches zero or one.

^ matches the start of a string (or line in multiline mode) and $ the end. \b matches a word boundary.

(?=...) is a positive lookahead that asserts what follows without consuming it; (?!...) is negative. Lookbehinds use (?<=...) and (?<!...).

(...) captures a match for reuse; (?:...) groups without capturing; (? ...) creates a named group.

Reference

(...) captures a match for reuse; (?:...) groups without capturing; (? ...) creates a named group.

Regular expression syntax at a glance. Click any card to copy the pattern.

Live Tester

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Test String

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