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🧵 Regex Cheatsheet

Anchors, character classes, quantifiers, flags, and real-world regex patterns you can paste into your next search.

Practical regex reference with search, one-click copy, and an inline tester.

Regex Tester

Validate patterns against sample text before deployment.

PatternFlagsSample textReplacement (optional)

Compiled as /^\w+$/g

Matches: 0

Control where matches begin and end.

Pattern	Meaning	Usage
`^`	Start of string or line	Anchor both ends for strict validation.
`$`	End of string or line	Useful for full-string matches.
`\b / \B`	Word boundary / non-boundary	Match standalone keywords.
`\A / \Z`	Absolute start / end	Some engines support these outside JS.

Build expressive token classes.

Pattern	Meaning	Usage
`.`	Any char except newline	Use dotall (s) to include newlines.
`[abc]`	Character set	Use ranges such as [a-zA-Z].
`\d \w \s`	Digit, word char, whitespace	Uppercase forms negate classes.
`(?:...)`	Non-capturing group	Groups without backreferences.

Define repetition counts.

Pattern	Meaning	Usage
`*`	0 or more	Use *? for lazy matching.
`+`	1 or more	Required repeated token.
`?`	0 or 1	Optional token.
`{min,max}`	Explicit bounds	Example: {8,} for minimum length.

Assert context without consuming characters.

Pattern	Meaning	Usage
`(?=...)`	Positive lookahead	Ensure next pattern exists.
`(?!...)`	Negative lookahead	Ensure next pattern does not exist.
`(?<=...)`	Positive lookbehind	Match text preceded by pattern.
`\1 \2`	Backreferences	Reuse captured groups.

Common starter expressions.

Pattern	Meaning	Usage
`^[a-z0-9_-]{3,16}$`	Username (3-16 chars)	Allows letters, digits, underscore, hyphen.
`^\+?[0-9\s-]{7,}$`	Flexible phone	Optional plus, spaces, dashes.
`^[\w.-]+@[\w.-]+\.[a-z]{2,}$`	Email-like string	Lightweight client-side validation.
`^https?:\/\/[\w.-]+`	HTTP/HTTPS URL	Fast scheme + domain check.

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