Essential Regex Patterns for Numbers, Text, and Common Data Formats

Check Numbers

Number: ^[0-9]*$

n digits: ^\d{n}$

At least n digits: ^\d{n,}$

m~n digits: ^\d{m,n}$

Number starting with zero or non‑zero: ^(0|[1-9][0-9]*)$

Non‑zero start with up to two decimal places: ^([1-9][0-9]*)+(.[0-9]{1,2})?$

Positive or negative number with 1‑2 decimal places: ^(\-)?\d+(\.\d{1,2})?$

Positive, negative and decimal numbers: ^(\-|\+)?\d+(\.\d+)?$

Non‑zero positive integer: ^[1-9]\d*$ or ^([1-9][0-9]*){1,3}$ or ^\+?[1-9][0-9]*$

Non‑zero negative integer: ^\-[1-9][]0-9"*$ or ^-[1-9]\d*$

Positive floating‑point number: ^[1-9]\d*\.\d*|0\.\d*[1-9]\d*$ or ^(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*))$

Negative floating‑point number: ^-([1-9]\d*\.\d*|0\.\d*[1-9]\d*)$ or ^(-(([0-9]+\.[0-9]*[1-9][0-9]*)|([0-9]*[1-9][0-9]*\.[0-9]+)|([0-9]*[1-9][0-9]*)))$

Check Characters

English letters: ^[A-Za-z]+$

Any characters, length 3‑20: ^.{3,20}$

String of 26 letters: ^[A-Za-z]+$

Lowercase letters only: ^[a-z]+$

Alphanumeric characters: ^[A-Za-z0-9]+$

Alphanumeric or underscore: ^\w+$ or ^\w{3,20}

Match any character except newline: .* (excludes \n )

Special Expressions

Email address: ^\w+([-+.]\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*$

Domain name: [a-zA-Z0-9][-a-zA-Z0-9]{0,62}(/.[a-zA-Z0-9][-a-zA-Z0-9]{0,62})+/.?

URL: [a-zA-z]+://[^\s]* or ^http://([\w-]+\.)+[\w-]+(/[\w-./?%&=]*)?$ or (?:(?:http://)|(?:https://))?(?:[\w](?:[\w\-]{0,61}[\w])?\.)+[a-zA-Z]{2,6}(?:/)

Phone number (various formats): ^(\(\d{3,4}-)|\d{3.4}-)?\d{7,8}$

Identity card number (15 or 18 digits): ^\d{15}|\d{18}$

Short ID (digits ending with optional x): ^([0-9]){7,18}(x|X)?$ or ^\d{8,18}|[0-9x]{8,18}|[0-9X]{8,18}?$

Account validity (starts with letter, 5‑16 characters, letters/digits/underscore): ^[a-zA-Z][a-zA-Z0-9_]{4,15}$

Password (starts with letter, 6‑18 characters, letters/digits/underscore): ^[a-zA-Z]\w{5,17}$

Strong password (8‑10 chars, includes upper, lower, digit, no special chars): ^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,10}$

Date format: \d{4}(?:-|\/|.)\d{1,2}(?:-|\/|.)\d{1,2}

Month (01‑12): ^(0?[1-9]|1[0-2])$

Day of month (01‑31): ^((0?[1-9])|((1|2)[0-9])|30|31)$

XML file name: ^([a-zA-Z]+-?)+[a-zA-Z0-9]+\.[xX][mM][lL]$

IPv4 address: ((?:(?:25[0-5]|2[0-4]\d|[01]?\d?\d)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d?\d))

IPv6 address: (([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))

Subnet mask: ((?:(?:25[0-5]|2[0-4]\d|[01]?\d?\d)\.){3}(?:25[0-5]|2[0-4]\d|[01]?\d?\d))