Regex Cheat Sheet: Patterns Every Developer Needs

Regular expressions feel like dark magic until you learn the patterns. Once you do, they become indispensable for text search, validation, data extraction, and string manipulation.

Grab a pattern, paste it into our Regex Tester to experiment, and adapt it to your needs.

Core Regex Syntax

Character Classes

Pattern	Matches	Example
`.`	Any character except newline	`a.c` matches "abc", "a1c"
`\d`	Any digit (0-9)	`\d{3}` matches "123"
`\w`	Word character (letter, digit, underscore)	`\w+` matches "hello_1"
`\s`	Whitespace	`\s+` matches spaces
`[abc]`	Any one of a, b, or c	`[aeiou]` matches vowels
`[^abc]`	Any character except a, b, c	`[^0-9]` matches non-digits
`[a-z]`	Any character in range	`[A-Za-z]` matches letters

Quantifiers

Pattern	Meaning
`*`	Zero or more
`+`	One or more
`?`	Zero or one
`{n}`	Exactly n times
`{n,m}`	Between n and m times

Anchors and Groups

Pattern	Meaning
`^`	Start of string
`$`	End of string
`\b`	Word boundary
`(abc)`	Capturing group
`(?:abc)`	Non-capturing group
`a\|b`	Alternation (or)
`(?=abc)`	Positive lookahead

Practical Patterns

Email Validation

^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$

URL Matching

https?:\/\/[\w.-]+(?:\.[a-zA-Z]{2,})(?:\/[\w./?%&=-]*)?

Password Strength

At least 8 characters, one uppercase, one lowercase, one digit, one special character:

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

For generating strong passwords, use our Password Generator.

Hex Color Codes

^#?([0-9A-Fa-f]{3}|[0-9A-Fa-f]{6})$

Convert between color formats with our Color Converter.

UUID Validation

^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$

Generate valid UUIDs with our UUID Generator.

Regex Performance Tips

Be specific — [a-zA-Z] is faster than .
Avoid catastrophic backtracking — Nested quantifiers like (a+)+ cause exponential time
Use non-capturing groups when you do not need the value
Anchor your patterns — ^pattern$ is faster than unanchored search
Test with edge cases — Use our Regex Tester before deploying

Frequently Asked Questions

What is the difference between `*` and `+`?

* matches zero or more occurrences, + requires at least one. So ab*c matches "ac" but ab+c does not.

How do I make regex case-insensitive?

Use the i flag: /pattern/i in JavaScript, re.IGNORECASE in Python.

Related Resources

Regex for Email Validation — patterns that work in production
Regex Tester Tool — test and debug patterns in real-time
Password Generator — generate passwords matching regex rules
UUID Generator — generate valid UUIDs