Mastering Regex: Essential Patterns for Validating Numbers, Emails, URLs, and More

1. Numeric Validation Expressions

Digits:

^[0-9]*$

n‑digit number:

^\d{n}$

At least n digits:

^\d{n,}$

m‑n digits:

^\d{m,n}$

Zero or non‑zero leading number:

^(0|[1-9][0-9]*)$

Non‑zero number with up to two decimal places:

^([1-9][0-9]*)+(\.[0-9]{1,2})?$

Positive/negative number with 1‑2 decimal places:

^(\-)?\d+(\.\d{1,2})?$

Signed number with optional decimal:

^(\-|\+)?\d+(\.\d+)?$

Positive integer (non‑zero):

^[1-9]\d*$

or

^([1-9][0-9]*){1,3}$

or

^\+?[1-9][0-9]*$

Negative integer:

^\-[1-9]\d*$

Non‑negative integer:

^\d+$

or

^[1-9]\d*|0$

Non‑positive integer:

^-?[1-9]\d*|0$

or

^((\-\d+)|(0+))$

Non‑negative floating number:

^\d+(\.\d+)?$

or

^[1-9]\d*\.\d*|0\.\d*[1-9]\d*|0?\.0+|0$

Non‑positive floating number:

^((\-\d+(\.\d+)?)|(0+(\.0+)?))$

or

^(-([1-9]\d*\.\d*|0\.\d*[1-9]\d*))|0?\.0+|0$

Positive floating 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 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]*)))$

General floating number:

^(-?\d+)(\.\d+)?$

or

^-?([1-9]\d*\.\d*|0\.\d*[1-9]\d*|0?\.0+|0)$

2. 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 only:

^[A-Za-z0-9]+$

Alphanumeric with underscore:

^\w+$

or

^\w{3,20}$

Chinese, English, digits, underscore:

^[\u4E00-\u9FA5A-Za-z0-9_]+$

Chinese, English, digits (no underscore):

^[\u4E00-\u9FA5A-Za-z0-9]+$

or

^[\u4E00-\u9FA5A-Za-z0-9]{2,20}$

Allow specific punctuation (% & ', ; = ? $ "):

^[^%&',;=?$\x22]+

Disallow tilde (~):

[^~\x22]+

3. 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[5|7]|15[0-9]|18[0-9])\d{8}$

Telephone number (various formats):

^(\(\d{3,4}-\)|\d{3,4}-)?\d{7,8}$

Chinese ID number (15 or 18 digits):

^\d{15}|\d{18}$

Short ID (digits, optional trailing x/X):

^([0-9]){7,18}(x|X)?$

or

^\d{8,18}|[0-9x]{8,18}|[0-9X]{8,18}?$

Account name (starts with letter, 5‑16 chars, letters/digits/underscore):

^[a-zA-Z][a-zA-Z0-9_]{4,15}$

Password (starts with letter, 6‑18 chars, letters/digits/underscore):

^[a-zA-Z]\w{5,17}$

Strong password (8‑10 chars, must include upper‑case, lower‑case, digit, no special chars):

^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,10}$

Date (yyyy‑mm‑dd, leap‑year aware):

^\d{4}-\d{1,2}-\d{1,2}$

Month (01‑12 or 1‑12):

^(0?[1-9]|1[0-2])$

Day of month (01‑31):

^((0?[1-9])|((1|2)[0-9])|30|31)$

Money format (optional commas, optional 1‑2 decimal places):

^[0-9]{1,3}(,[0-9]{3})*(\.[0-9]{1,2})?$

XML file name:

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

Chinese character regex:

[\u4e00-\u9fa5]

Double‑byte character:

^\x00-\xff

Blank line removal:

\n\s*\r

HTML tag regex (simplified):

<(\S?)[^>]>.*?</\1>|<.*?\/>

Trim leading/trailing whitespace:

^\s|\s$

QQ number (starts with non‑zero, at least 5 digits):

[1-9][0-9]{4,}

Chinese postal code (6 digits):

[1-9]\d{5}(?!\d)

IPv4 address (basic):

\d+\.\d+\.\d+\.\d+

IPv4 address (full validation):

((?:(?: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))