Very useful regular expression quick reference

flags

• g - global match
• i - ignore case
• m - match over multiple lines

Escaping

• \ - special characters to literal and literal characters to special

Quantifiers

• ? - matches zero or one times
• * - matches zero or more times
• + - matches one or more times
• {n} - matches n times
• {n, m} - matches at least n times, but not more than m times

Anchors

• ^ - matches at the start of the line
• $ - matches at the end of the line
• \b - matches at the beginning or the end of a word

delimiter

• (?:x) - matches x not remember the match
• x(?=y) - matches x only if x is followed by y
• x(?!y) - matches x only if x is not followed by y

Character Escapes

• \s - matches whitespace
• \S - matches anything but a whitespace
• \f - matches a form-feed
• \n - matches a linefeed
• \r - matches a carriage return
• \t - matches a horizontal tab
• \v - matches vertical tab
• \w - matches any alphanumeric character including the underscore. Equivalent to [A-Za-z0-9_]
• \W - matches any non-word character. Equivalent to [^A-Za-z0-9_]

Others

• . - matches any character except a newline