📖 Guide

Regex Cheat Sheet — Complete Regular Expression Reference

Every regex pattern, syntax, and technique you need in this cheat sheet. From basics to advanced lookaheads, with real examples.

88 commands across 10 categories

Related tool:Regex Tester →

Character Classes Anchors Quantifiers Groups & Capturing Lookahead & Lookbehind Alternation & Logic Flags / Modifiers Common Patterns JavaScript String Methods Advanced Techniques

Building an email field? The "Email address (basic)" pattern below is a quick reference, not a production-ready check — see our email validation regex deep-dive for which patterns wrongly reject real addresses and what to use instead.

Command	Description
`.`	Match any character except newline
`\d` e.g. \d{3} → 123	Match any digit [0-9]
`\D`	Match any non-digit
`\w`	Match word character [a-zA-Z0-9_]
`\W`	Match non-word character
`\s`	Match whitespace (space, tab, newline)
`\S`	Match non-whitespace
`[abc]` e.g. [aeiou] → vowels	Match any character in the set
`[^abc]`	Match any character NOT in the set
`[a-z]`	Match character range (lowercase letters)
`[a-zA-Z0-9]`	Match alphanumeric characters
`[\d\s]`	Combine classes — digit or whitespace
`\t`	Match tab character
`\n`	Match newline character
`\\`	Match literal backslash
`\.`	Match literal dot (escaped metacharacter)

Command	Description
`^` e.g. ^Hello → matches 'Hello world'	Start of string (or line with m flag)
`$` e.g. world$ → matches 'Hello world'	End of string (or line with m flag)
`\b` e.g. \bcat\b → 'cat' but not 'category'	Word boundary
`\B`	Not a word boundary
`\A`	Start of string (not affected by multiline flag)
`\Z`	End of string (not affected by multiline flag)

Command	Description
`` e.g. a → '', 'a', 'aaa'	Match 0 or more (greedy)
`+` e.g. a+ → 'a', 'aaa'	Match 1 or more (greedy)
`?` e.g. colou?r → 'color', 'colour'	Match 0 or 1 (optional)
`{n}` e.g. \d{4} → '2024'	Match exactly n times
`{n,}` e.g. \d{2,} → '42', '123'	Match n or more times
`{n,m}` e.g. \d{2,4} → '42', '123', '1234'	Match between n and m times
`*?`	Match 0 or more (lazy/non-greedy)
`+?`	Match 1 or more (lazy/non-greedy)
`??`	Match 0 or 1 (lazy)
`{n,m}?`	Match between n and m (lazy)

Command	Description
`(pattern)` e.g. (\d{3})-(\d{4})	Capturing group — captures the match
`(?:pattern)`	Non-capturing group — groups without capturing
`(?<name>pattern)` e.g. (?<year>\d{4})-(?<month>\d{2})	Named capturing group
`\1, \2` e.g. (\w+)\s\1 → 'the the'	Backreference to captured group
`\k<name>`	Backreference by name
`$1, $2`	Reference captured group in replacement string
`$&`	Reference entire match in replacement
$`	Reference text before match in replacement
`$'`	Reference text after match in replacement

Command	Description
`(?=pattern)` e.g. \d(?=px) → '5' in '5px'	Positive lookahead — match if followed by pattern
`(?!pattern)` e.g. \d(?!px) → '3' in '3em'	Negative lookahead — match if NOT followed by pattern
`(?<=pattern)` e.g. (?<=\$)\d+ → '100' in '$100'	Positive lookbehind — match if preceded by pattern
`(?<!pattern)`	Negative lookbehind — match if NOT preceded by pattern
`(?<=\$)\d+(?=\.\d{2})` e.g. '$19.99' → '19'	Combined lookaround — dollar amount

Command	Description
`a\|b` e.g. cat\|dog → 'cat' or 'dog'	Match a OR b
`(a\|b)c` e.g. (re\|un)do → 'redo' or 'undo'	Group alternation with continuation
`(?:jpg\|png\|gif)` e.g. \.(jpg\|png\|gif)$	Non-capturing alternation

Command	Description
`g`	Global — find all matches, not just the first
`i`	Case-insensitive matching
`m`	Multiline — ^ and $ match line starts/ends
`s`	Dotall — . matches newline characters too
`u`	Unicode — enable full Unicode matching
`y`	Sticky — match only at lastIndex position (JS)
`d`	Has indices — include match index info (JS)
`(?i)`	Inline flag — enable case-insensitive in pattern

Command	Description
`^[\w.-]+@[\w.-]+\.\w{2,}$`	Email address (basic)
`https?://[\w.-]+(?:\.[\w]{2,})(?:/\S*)?`	URL (HTTP/HTTPS)
`^\d{1,3}(\.\d{1,3}){3}$`	IPv4 address
`^\+?\d{1,3}[-.\s]?\(?\d{1,4}\)?[-.\s]?\d{3,4}[-.\s]?\d{3,4}$`	Phone number (international)
`^\d{4}-\d{2}-\d{2}$` e.g. 2024-01-15	Date (YYYY-MM-DD)
`^\d{2}/\d{2}/\d{4}$`	Date (DD/MM/YYYY)
`^#?([0-9a-fA-F]{3}\|[0-9a-fA-F]{6})$` e.g. #ff0000, #f00	Hex color code
`^(?=.[a-z])(?=.[A-Z])(?=.*\d).{8,}$`	Strong password (8+ chars, upper, lower, digit)
`^[a-z0-9-]+$`	URL slug (lowercase, numbers, hyphens)
`<[^>]+>`	HTML tag (basic)
`\b\d{1,3}(,\d{3})*(\.\d+)?\b` e.g. 1,234,567.89	Number with commas
`^\s+\|\s+$`	Leading/trailing whitespace (for trimming)
`\s{2,}`	Multiple consecutive whitespace

Command	Description
`str.match(/pattern/g)` e.g. 'abc 123'.match(/\d+/g) → ['123']	Find all matches, return array
`str.matchAll(/pattern/g)`	Iterator of all matches with groups
`str.search(/pattern/)`	Return index of first match (-1 if none)
`str.replace(/pattern/, 'new')`	Replace first match
`str.replace(/pattern/g, 'new')`	Replace all matches
`str.replaceAll('old', 'new')`	Replace all (string or regex with g flag)
`/pattern/.test(str)` e.g. /^\d+$/.test('123') → true	Return true/false if pattern matches
`/pattern/.exec(str)`	Return match object with groups and index
`str.split(/pattern/)` e.g. 'a, b, c'.split(/,\s*/)	Split string by regex
`new RegExp('pattern', 'flags')`	Create regex from string (for dynamic patterns)

Command	Description
`(?:(?!pattern).)*`	Tempered greedy token — match anything not containing pattern
`\p{L}` e.g. /\p{L}+/gu	Unicode letter (any language, requires u flag)
`\p{N}`	Unicode number (any script)
`\p{Emoji}`	Match emoji characters (requires u flag)
`(?<=(\d+))\s(?=\w)`	Complex lookaround combination
`^(?!.forbidden).$`	Match line NOT containing word
`(.)\1+` e.g. 'aaa' → 'aaa'	Match repeated characters
`(?=.a)(?=.b)(?=.*c)`	Match string containing all of a, b, and c (any order)

Regex Cheat Sheet — Complete Regular Expression Reference

Character Classes

Anchors

Quantifiers

Groups & Capturing

Lookahead & Lookbehind

Alternation & Logic

Flags / Modifiers

Common Patterns

JavaScript String Methods

Advanced Techniques

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