Regex Patterns Quick Start

Quickly craft regular expressions for validation and parsing.

Character Classes

Character classes match a single character from a specified set.

Pattern	Description
`\d`	Matches any digit (equivalent to `[0-9]`)
`\w`	Matches any word character (letters, numbers, underscores)
`\s`	Matches any whitespace character (space, tab, newline)
`\D`	Matches any NON-digit
`\W`	Matches any NON-word character
`.`	Matches ANY character except newline

Quantifiers

Quantifiers specify how many times the preceding element should match.

Pattern	Description
`*`	0 or more times
`+`	1 or more times
`?`	0 or 1 time (optional)
`{3}`	Exactly 3 times
`{3,}`	3 or more times
`{3,5}`	3 to 5 times

Anchors and Boundaries

^     # Start of string (or line in multi-line mode)
$     # End of string (or line in multi-line mode)
\b    # Word boundary (matches position between \w and \W)

Common Practical Regex Patterns

[!IMPORTANT] Always test your regex patterns using tools like regexr.com before putting them into production!

Email Validation

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

Password Strength

(Minimum 8 characters, at least one uppercase letter, one lowercase letter, and one number)

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

URL Extraction

^https?:\/\/(?:www\.)?[-a-zA-Z0-9@:%._\+~#=]{1,256}\.[a-zA-Z0-9()]{1,6}\b(?:[-a-zA-Z0-9()@:%_\+.~#?&\/=]*)$

Extracting Hex Colors

^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$

Groups and Capturing

Use parentheses () to group parts of a pattern together and extract them.

# Match a date in YYYY-MM-DD format and capture the parts
(\d{4})-(\d{2})-(\d{2})

ACM VJIT