Regex Cheatsheet

Match exact text. Case-sensitive by default.

hello

Example: Say hello world

The i flag makes the match case-insensitive.

/hello/i

Example: Hello HELLO hello

. matches any single character except newline.

h.llo

Example: hello hallo hxllo

^ anchors the match to the start of the string.

^hello

Example: hello world (not: say hello)

$ anchors the match to the end of the string.

world$

Example: hello world (not: world class)

\b matches at a word boundary.

\bcat\b

Example: cat (not: category, scatter)

* matches 0 or more of the preceding element.

ab*c

Example: ac, abc, abbc, abbbc

+ matches 1 or more of the preceding element.

ab+c

Example: abc, abbc (not: ac)

? makes the preceding element optional.

colou?r

Example: color, colour

{n} matches exactly n repetitions.

\d{4}

Example: 2024, 1999

{n,m} matches between n and m repetitions.

\d{2,4}

Example: 12, 123, 1234

\d matches any digit. \D matches non-digit.

\d

Example: 0-9

\w matches word characters. \W matches non-word.

\w

Example: a-z, A-Z, 0-9, _

\s matches whitespace. \S matches non-whitespace.

\s

Example: space, tab, newline

[] defines a character set. Match any one character listed.

[aeiou]

Example: a, e, i, o, u

^ inside [] negates the set.

[^0-9]

Example: any non-digit

() captures matched text for backreferences or extraction.

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

Example: 2024-03-15 → groups: 2024, 03, 15

(?:) groups without capturing.

(?:https?://)

Example: http:// or https://

(?<name>) creates a named capture group.

(?<year>\d{4})-(?<month>\d{2})

Example: groups.year, groups.month

| acts as OR between alternatives.

cat|dog|bird

Example: cat, dog, bird

(?=...) asserts what follows without consuming it.

\d+(?= dollars)

Example: 100 in '100 dollars'

(?!...) asserts what does NOT follow.

\d+(?! dollars)

Example: 100 in '100 euros'

Basic email validation pattern.

[\w.-]+@[\w.-]+\.[a-z]{2,}

Example: user@example.com

Simple URL matching pattern.

https?://[\w.-]+(?:\.[a-z]{2,})+(?:/[\S]*)?

Example: https://example.com/path

Match an IPv4 address (does not validate range 0-255).

(?:\d{1,3}\.){3}\d{1,3}

Example: 192.168.1.1

Match hex color codes.

#[0-9A-Fa-f]{3,6}

Example: #fff, #3a7bcd