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Regular Expressions Cheatsheet

Basic Patterns​

  • . - Any character except newline
  • \w - Word character [A-Za-z0-9_]
  • \W - Non-word character
  • \d - Digit [0-9]
  • \D - Non-digit
  • \s - Whitespace (space, tab, newline)
  • \S - Non-whitespace
  • \b - Word boundary
  • \B - Non-word boundary

Anchors​

  • ^ - Start of string/line
  • $ - End of string/line
  • \A - Start of string only
  • \Z - End of string only

Character Classes​

  • [abc] - Any character a, b, or c
  • [^abc] - Any character except a, b, c
  • [a-z] - Any lowercase letter
  • [A-Z] - Any uppercase letter
  • [0-9] - Any digit
  • [a-zA-Z] - Any letter
  • [a-zA-Z0-9] - Any letter or digit

Quantifiers​

  • * - 0 or more
  • + - 1 or more
  • ? - 0 or 1
  • {n} - Exactly n times
  • {n,} - n or more times
  • {n,m} - Between n and m times
  • *? - Lazy match (0 or more)
  • +? - Lazy match (1 or more)

Groups and References​

  • (...) - Capturing group
  • (?:...) - Non-capturing group
  • (?<name>...) - Named capturing group
  • \1, \2 - Backreference to group
  • \k<name> - Backreference to named group

Alternation​

  • | - OR operator
  • (?:|) - OR in non-capturing group

Lookarounds​

  • (?=...) - Positive lookahead
  • (?!...) - Negative lookahead
  • (?<=...) - Positive lookbehind
  • (?<!...) - Negative lookbehind

Common Patterns​

# Email
^[\w\.-]+@[\w\.-]+\.\w+$

# URL
^(https?:\/\/)?([\da-z\.-]+)\.([a-z\.]{2,6})([\/\w \.-]*)*\/?$

# Phone Number (US)
^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$

# Date (YYYY-MM-DD)
^\d{4}-(0[1-9]|1[0-2])-(0[1-9]|[12]\d|3[01])$

# Strong Password
^(?=.*[A-Za-z])(?=.*\d)(?=.*[@$!%*#?&])[A-Za-z\d@$!%*#?&]{8,}$

Modifiers​

  • i - Case-insensitive
  • g - Global search
  • m - Multiline
  • s - Single line (dot matches newline)
  • u - Unicode
  • y - Sticky search

Special Characters Escaping​

  • \. - Literal dot
  • \* - Literal asterisk
  • \+ - Literal plus
  • \? - Literal question mark
  • \[ - Literal square bracket
  • \( - Literal parenthesis
  • \\ - Literal backslash