A pattern for matching text strings. Powerful for searching, validating, and manipulating text.

What flavors are supported?

JavaScript regex (ECMAScript), compatible with most modern languages.

Start with basics: . (any char), * (zero+), + (one+), [] (class), () (groups). Practice here.

What is the difference between greedy and lazy regex matching?

Greedy quantifiers (*, +) match as much text as possible. Lazy quantifiers (*?, +?) match as little as possible. For example, matches the entire string ' ', while matches only ' '.

How do I match an email address with regex?

A basic email regex is [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}. However, the full RFC 5322 email spec is extremely complex. For production use, prefer your language's built-in email validation.

Regex Tester

Test regular expressions with real-time matching

/ /

g (global) i (ignore case) m (multiline) s (dotall)

Test String

Matches: 0

Groups: 0

Result (highlights)

Common Patterns

Regex Quick Reference

. Any character except newline

\d Digit (0-9) \w Word character \s Whitespace

* 0 or more + 1 or more ? 0 or 1

^ Start of string $ End of string

[abc] Character class (abc) Capturing group

Flags

g Global - find all matches

i Case-insensitive matching

m Multiline - ^ and $ match line boundaries

s Dotall - . matches newlines too

Regex Tester

Common Patterns

Regex Quick Reference

Flags

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