Regex Cheatsheet & Builder

Browse a searchable regex syntax reference and snippet library for common patterns like email, URL, IP, and date, with copyable expressions.

Regex reference

SearchFilter tokens, snippets, and descriptions

Ready-made patterns

^[\w.+-]+@[\w-]+\.[\w.-]+$

Pragmatic email address match (not RFC-exhaustive).

URL (http/https)

https?:\/\/[\w.-]+(?:\.[\w.-]+)+[\w\-._~:/?#[\]@!$&'()*+,;=]*

Matches http or https URLs.

IPv4 address

\b(?:(?:25[0-5]|2[0-4]\d|1?\d?\d)\.){3}(?:25[0-5]|2[0-4]\d|1?\d?\d)\b

Matches a valid IPv4 address (0-255 per octet).

Date (YYYY-MM-DD)

\b\d{4}-(?:0[1-9]|1[0-2])-(?:0[1-9]|[12]\d|3[01])\b

ISO-style date with basic month/day range checks.

Time (HH:MM 24h)

\b(?:[01]\d|2[0-3]):[0-5]\d\b

24-hour time, optionally extend with :ss.

Hex color

#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})\b

Matches #fff or #ffffff style hex colors.

Slug

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

Lowercase, hyphen-separated URL slug.

UUID v4

\b[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-4[0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}\b

Matches a version-4 UUID.

US phone

$?\d{3}$?[-.\s]?\d{3}[-.\s]?\d{4}

Common US phone number formats.

Strong password

^(?=.*[a-z])(?=.*[A-Z])(?=.*\d)(?=.*[^\w\s]).{8,}$

At least 8 chars with lower, upper, digit, and symbol.

Leading/trailing whitespace

^\s+|\s+$

Use with the g flag to trim each line.

Character classes

.Any character except newline

\dDigit (0-9)

\DNot a digit

\wWord character (a-z, A-Z, 0-9, _)

\WNot a word character

\sWhitespace (space, tab, newline)

\SNot whitespace

[abc]Any one of a, b, or c

[^abc]Any character except a, b, or c

[a-z]Character in the range a to z

Anchors & boundaries

^Start of string (or line in multiline mode)

$End of string (or line in multiline mode)

\bWord boundary

\BNot a word boundary

Quantifiers

*0 or more

+1 or more

?0 or 1 (optional)

{n}Exactly n times

{n,}n or more times

{n,m}Between n and m times

*?Lazy: as few as possible

Groups & lookarounds

(abc)Capturing group

(?:abc)Non-capturing group

(?<name>abc)Named capturing group

a|bAlternation: a or b

(?=abc)Positive lookahead

(?!abc)Negative lookahead

(?<=abc)Positive lookbehind

(?<!abc)Negative lookbehind

\1Backreference to group 1

Flags

gGlobal: find all matches

iCase-insensitive

mMultiline: ^ and $ match line breaks

sDotall: . matches newline

uUnicode mode

ySticky: match from lastIndex only

.env to JSON

Parse a .env / dotenv file into a JSON object and convert JSON back into .env format, handling quotes, comments, and export prefixes.

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.gitattributes Generator

Generate a .gitattributes file selecting line-ending normalization, binary, LFS and linguist rules from presets.

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.htaccess Redirect Builder

Build Apache .htaccess redirect rules (Redirect, RewriteRule) from source/target URL pairs with status codes.

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Accept-Language / Accept Parser

Parse and sort Accept-Language or Accept headers by quality value (q-factor).

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Regex Cheatsheet & Builder

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