Regex Cheatsheet

The ultimate regular expression reference. Common patterns for validation and a complete syntax guide for everyday use.

Ready-to-Use Patterns

Email Address

Matches standard email formats like user@example.com.

^[\w-\.]+@([\w-]+\.)+[\w-]{2,4}$

Strong Password

Min 8 chars, at least 1 letter and 1 number.

^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{8,}$

IPv4 Address

Matches valid IPv4 addresses (0.0.0.0 to 255.255.255.255).

^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$

Date (YYYY-MM-DD)

Matches ISO 8601 dates (e.g., 2023-12-31).

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

Hex Color

Matches 3 or 6 digit hex codes, optional #.

^#?([0-9a-fA-F]{3}|[0-9a-fA-F]{6})$

URL Slug

Lowercase letters, numbers, and hyphens only.

^[a-z0-9]+(?:-[a-z0-9]+)*$

Syntax Reference

Anchors

Symbol	Meaning	Example
^	Start of string/line	^Start
$	End of string/line	End$
\b	Word boundary	\bword\b

Quantifiers

Symbol	Meaning	Example
*	0 or more	a*
+	1 or more	a+
?	0 or 1	a?
{n}	Exactly n times	a{3}
{n,}	n or more times	a{3,}
{n,m}	Between n and m	a{3,6}

Character Classes

Symbol	Meaning	Example
.	Any character (except newline)	.
\d	Digit (0-9)	\d
\w	Word char (A-Z, a-z, 0-9, _)	\w
\s	Whitespace	\s
\D	Not a digit	\D
\W	Not a word char	\W
\S	Not whitespace	\S

Sets & Ranges

Symbol	Meaning	Example
[abc]	Any of a, b, or c	[abc]
[^abc]	None of a, b, or c	[^abc]
[a-z]	Char in range a-z	[a-z]

Groups

Symbol	Meaning	Example
(...)	Capture group	(abc)
(?:...)	Non-capturing group	(?:abc)
(?=...)	Positive lookahead	a(?=b)
(?!...)	Negative lookahead	a(?!b)

# Master Regex with Common Patterns and Syntax

Regular Expressions (Regex) are an incredibly powerful tool for text processing, validation, and searching. However, their cryptic syntax can be difficult to remember.

This Regex Cheatsheet helps you quickly find the code you need. Use the Ready-to-Use Patterns for common tasks like validating emails, passwords, and dates. If you are building your own regex, consult theSyntax Reference for a clear explanation of anchors, quantifiers, and character classes.

Tips for Learning Regex

Start simple: Match literal characters first.
Use tools like our Regex Tester to experiment.
Break complex patterns down into smaller groups.