Regex Cheat Sheet

^

# Match only at the beginning of the input.

$

# Match only at the end of the input.

\b

# Match a transition between word and non-word characters.

\B

# Match where a word boundary does not occur.

\A

# Match only at the absolute start of the entire string.

\Z

# Match only at the absolute end of the entire string.

\d

# Match one ASCII digit character.

\D

# Match one non-digit character.

\w

# Match a word character.

\W

# Match a non-word character.

\s

# Match one whitespace character.

\S

# Match one non-whitespace character.

[a-z]

# Match one lowercase Latin letter.

[^0-9]

# Match one character not in the set.

[-_]

# Match a hyphen or underscore.

\p{L}

# Match any Unicode letter.

\p{N}

# Match any Unicode number.

ab*

# Repeat the previous token any number of times.

ab+

# Repeat the previous token at least once.

colou?r

# Make the previous token optional.

\d{4}

# Match an exact number of repetitions.

\w{3,10}

# Match between a minimum and maximum number of repetitions.

\d{2,}

# Match at least a minimum number of repetitions.

<.*?>

# Use the shortest possible match.

".+?"

# Use the shortest possible `+` match.

\d++

# Repeat without backtracking.

(\d{4})-(\d{2})-(\d{2})

# Capture a submatch for reuse or extraction.

(?:cat|dog)

# Group without creating a numbered capture.

error|warning|info

# Match one branch or another.

^(?:https?|ftp)://([^/\s]+)

# Combine multiple grouped pieces.

^(?:\+1[-.\s]?)?\d{3}[-.\s]?\d{3}[-.\s]?\d{4}$

# Make an entire grouped piece optional.

(?|(Mr|Ms)\.?\s+(\w+)|(Dr)\.?\s+(\w+))

# Reset group numbers per alternation branch.

\b(\w+)\s+\1\b

# Match the same word twice in a row.

(["\']).*?\1

# Require the closing quote to match the opener.

<([A-Za-z][A-Za-z0-9]*)\b[^>]*>.*?</\1>

# Require the same tag name at both ends.

(?<word>\w+)\s+\k<word>

# Reuse a named capture later in the pattern.

\w+(?=:)

# Require text to follow the current position.

foo(?!bar)

# Require text not to follow the current position.

(?<=\$)\d+(?:\.\d{2})?

# Require text to precede the current position.

(?<!\$)\b\d+\b

# Require text not to precede the current position.

(?:(?!END).)+

# Match any text until a stopper without over-consuming.

(?i)error

# Enable case-insensitive matching.

(?m)^ERROR:

# Let `^` and `$` work per line.

(?s)<script.*?</script>

# Let dot match newlines.

(?x) ^ \d{4} - \d{2} - \d{2} $

# Allow whitespace and comments inside the regex.

(?u)\b\p{L}+\b

# Enable Unicode-aware parsing or matching.

(?i:api)-v[0-9]+

# Enable or disable flags for only part of a pattern.

\.

# Match an actual period character.

\\

# Match a backslash character.

[\^\$\.\|\?\*\+\(\)\{\}]

# Match literal regex metacharacters.

\Q[a-z]+(foo)?\E

# Treat a whole block as literal text.

(?>\d{4}-\d{2}-\d{2})

# Prevent backtracking into a grouped subpattern.

[A-Z]++

# Consume as much as possible without backtracking.

(.*a)*

# Example of a risky pattern to rewrite.

<title>[^<]*</title>

# Use explicit stop characters instead of dot-star where possible.