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Regex Cheatsheet

See the core regex syntax — character classes, quantifiers, anchors, groups, and more — presented as a pattern, description, and example trio for quick reading. Use the search box to filter by keyword while coding, so you can look up the exact syntax you need without leaving your workflow.

Regex Tester

Pattern

Test String

Matches: 0

Character Classes

Pattern	Description	Example
`.`	Any character except newline	`c.t → cat, cut, c4t`
`\d`	Digit (0–9)	`\d+ → 123, 42`
`\D`	Non-digit	`\D+ → abc, !@#`
`\w`	Word character [a-zA-Z0-9_]	`\w+ → hello_1`
`\W`	Non-word character	`\W → space, !`
`\s`	Whitespace (space, tab, newline)	`a\sb → a b`
`\S`	Non-whitespace	`\S+ → hello`
`[abc]`	Any character in the set	`[aeiou] → vowels`
`[^abc]`	Any character not in the set	`[^0-9] → non-digits`
`[a-z]`	Character in range	`[a-z] → lowercase`

Quantifiers

Pattern	Description	Example
`*`	Zero or more times	`ab* → a, ab, abb`
`+`	One or more times	`ab+ → ab, abb`
`?`	Zero or one time	`colou?r → color, colour`
`{n}`	Exactly n times	`\d{3} → 123`
`{n,}`	n or more times	`\d{2,} → 12, 123`
`{n,m}`	Between n and m times	`\d{2,4} → 12, 1234`
`*?`	Zero or more, lazy (non-greedy)	`<.*?> → <a>`
`+?`	One or more, lazy	`<.+?> → <b>`

Anchors

Pattern	Description	Example
`^`	Start of string or line	`^Hello → "Hello world"`
`$`	End of string or line	`world$ → "Hello world"`
`\b`	Word boundary	`\bcat\b → "the cat sat"`
`\B`	Non-word boundary	`\Bcat → "concatenate"`

Groups & References

Pattern	Description	Example
`(abc)`	Capturing group	`(ab)+ → ababab`
`(?:abc)`	Non-capturing group	`(?:ab)+ → ababab`
`(?=abc)`	Positive lookahead	`foo(?=bar) → foobar`
`(?!abc)`	Negative lookahead	`foo(?!bar) → foobaz`
`a\|b`	a or b	`cat\|dog → cat, dog`
`\1`	Backreference to group 1	`(\w)\1 → aa, bb`

Common Patterns

Pattern	Description	Example
`^[\w.+\-]+@[\w\-]+\.[a-zA-Z]{2,}$`	Email address	`user@example.com`
`^https?:\/\/[\w\-.]+(?:\.[\w\-.]+)+[\w\-._~:/?#[\]@!$&'()+,;=]$`	URL	`https://example.com`
`^\d{2,3}-\d{3,4}-\d{4}$`	Korean phone number	`010-1234-5678`
`^\d{4}-\d{2}-\d{2}$`	ISO date (YYYY-MM-DD)	`2024-01-15`
`^[a-zA-Z0-9]{6,20}$`	Alphanumeric ID (6–20 chars)	`user123`
`^(?=.[a-z])(?=.[A-Z])(?=.*\d).{8,}$`	Strong password (upper+lower+digit, 8+)	`Passw0rd`
`^#([A-Fa-f0-9]{6}\|[A-Fa-f0-9]{3})$`	HEX color code	`#FF5733 or #F53`
`^\d{1,3}(\.\d{1,3}){3}$`	IPv4 address	`192.168.1.1`

Related Tools

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HTML Entities Reference

Find HTML entities for reserved characters like &, <, and >, as well as copyright symbols, arrows, and mathematical operators — each shown with both its named and numeric code. Search by character or description to locate the entity you need, then click to copy the code to your clipboard for immediate use in HTML or CSS.

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FAQ

Do I really need to learn regex?▼

Very useful for programming, data analysis, and text editors. It automates repetitive text tasks like email validation, phone extraction, and log analysis.

What are the most commonly used regex patterns?▼

Email validation, URL matching, phone number extraction, number extraction (\d+), and whitespace removal (\s+) are the most common.