Common Regular Expressions for Validating Numbers, Characters, and Special Formats

Number Validation Expressions

Any digit (including empty): ^[0-9]*$

Exactly n digits: ^\d{n}$

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

Between m and n digits: ^\d{m,n}$

Zero or non‑zero leading digits: ^(0|[1-9][0-9]*)$

Non‑zero integer 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})$

Signed number with optional decimal part: ^(-|\+)?\d+(\.\d+)?$

Positive real number with exactly two decimal places: ^[0-9]+(\.[0-9]{2})?$

Positive real number with 1‑3 decimal places: ^[0-9]+(\.[0-9]{1,3})?$

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]*)$

Non‑negative integer (including zero): ^\d+$ or ^[1-9]\d*|0$

Non‑positive integer (including zero): ^-[1-9]\d*|0$ or ^((-\d+)|(0+))$

Non‑negative floating‑point number: ^\d+(\.\d+)?$ or complex alternatives

Non‑positive floating‑point number: ^((-\d+(\.\d+)?)|(0+(\.0+)?))$

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

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

General floating‑point number: ^(-?\d+)(\.\d+)?$

Character Validation Expressions

Chinese characters: ^[\u4e00-\u9fa5]{0,}$

Alphanumeric (letters and digits): ^[A-Za-z0-9]+$ or ^[A-Za-z0-9]{4,40}$

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

Only letters (A‑Z, a‑z): ^[A-Za-z]+$

Only uppercase letters: ^[A-Z]+$

Only lowercase letters: ^[a-z]+$

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

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

Chinese, letters, digits, underscore: ^[\u4E00-\u9FA5A-Za-z0-9_]+$

Chinese, letters, digits (no underscore): ^[\u4E00-\u9FA5A-Za-z0-9]+$ or ^[\u4E00-\u9FA5A-Za-z0-9]{2,20}$

Disallow tilde (~) character: [^~\x22]+

Special‑Requirement 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})+\.?/

Internet URL: [a-zA-z]+://[^\s]* or ^http://([\w-]+\.)+[\w-]+(/[\w-./?%&=]*)?$

Mobile phone number (China): ^(13[0-9]|14[57]|15[0-35-9]|18[0-9])\d{8}$

Landline telephone (e.g., 0511-4405222): \d{3}-\d{8}|\d{4}-\d{7}

Comprehensive telephone regex (supports mobile, area code, extension): ((\d{11})|^((\d{7,8})|(\d{4}|\d{3})-(\d{7,8})|(\d{4}|\d{3})-(\d{7,8})-(\d{4}|\d{3}|\d{2}|\d{1})|(\d{7,8})-(\d{4}|\d{3}|\d{2}|\d{1}))$)

Chinese ID number (15 or 18 digits, last may be X): (^\d{15}$)|(^\d{18}$)|(^\d{17}(\d|X|x)$)

Account name (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, must include upper, lower, digit, no special chars): ^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])[a-zA-Z0-9]{8,10}$

Strong password (8‑10 chars, may include special chars): ^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,10}$

Date format (YYYY‑M‑D): ^\d{4}-\d{1,2}-\d{1,2}

Month (01‑09 or 1‑12): ^(0?[1-9]|1[0-2])$

Day of month (01‑31): ^((0?[1-9])|([12][0-9])|30|31)$

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

Chinese character: [\u4e00-\u9fa5]

Blank line (for removal): \n\s*\r

HTML tag: <(\S*?)[^>]*>.*?|<.*?\s/\>

QQ number (starts from 10000): [1-9][0-9]{4,}

Chinese postal code (6 digits): [1-9]\d{5}(?!\d)

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