Essential Regular Expressions for Validating Numbers, Text, URLs and More

1. Number validation expressions

^[0-9]*$

– any number of digits (including empty). ^\d{n}$ – exactly n digits. ^\d{n,}$ – at least n digits. ^\d{m,n}$ – between m and n digits. ^(0|[1-9][0-9]*)$ – zero or a non‑zero‑leading integer. ^([1-9][0-9]*)+(\.[0-9]{1,2})?$ – non‑zero‑leading integer with up to two decimal places. ^(\-)?\d+(\.\d{1,2})?$ – optional sign, integer or decimal with 1‑2 fractional digits. ^(\-|\+)?\d+(\.\d+)?$ – signed integer or decimal. ^[0-9]+(\.[0-9]{2})?$ – integer with optional two‑digit fraction. ^[0-9]+(\.[0-9]{1,3})?$ – integer with optional 1‑3 digit fraction. ^[1-9]\d*$ – positive integer without leading zero. ^\-[1-9]\d*$ – negative integer without leading zero. ^\d+$ – non‑negative integer. ^\-?[1-9]\d*$ – non‑positive integer. ^\d+(\.\d+)?$ – non‑negative floating number. ^\-?(\d+)(\.\d+)?$ – signed floating number.

2. Character validation expressions

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

– Chinese characters. ^[A-Za-z0-9]+$ – alphanumeric. ^.{3,20}$ – any 3‑20 characters. ^[A-Za-z]+$ – letters only. ^[A-Z]+$ – uppercase letters. ^[a-z]+$ – lowercase letters. ^[A-Za-z0-9]+$ – letters and digits. ^\w+$ – word characters (letters, digits, underscore). ^[\u4E00-\u9FA5A-Za-z0-9_]+$ – Chinese, letters, digits, underscore. ^[\u4E00-\u9FA5A-Za-z0-9]+$ – Chinese, letters, digits (no underscore). [^%&',;=?$\x22]+ – excludes specific punctuation. [^~\x22]+ – excludes tilde.

3. Special‑requirement expressions

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

– email address.

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

– domain name. [a-zA-z]+://[^\s]* – generic URL. ^(13[0-9]|14[57]|15[0-9]|18[0-9])\d{8}$ – Chinese mobile number. ^(\(\d{3,4}-)|\d{3.4}-)?\d{7,8}$ – telephone number. \d{3}-\d{8}|\d{4}-\d{7} – landline number. ^\d{15}|\d{18}$ – ID card number. ^[a-zA-Z][a-zA-Z0-9_]{4,15}$ – username (letter start, 5‑16 chars). ^[a-zA-Z]\w{5,17}$ – password (letter start, 6‑18 chars). ^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,10}$ – strong password (mix of cases and digits). ^\d{4}-\d{1,2}-\d{1,2} – date format yyyy‑MM‑dd. ^(0?[1-9]|1[0-2])$ – month (01‑12). ^((0?[1-9])|((1|2)[0-9])|30|31)$ – day (01‑31).

4. Additional useful patterns

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

– XML file name. [\u4e00-\u9fa5] – single Chinese character. [^\x00-\xff] – double‑byte character. \n\s*\r – blank line. <(\S*?)[^>]*>.*?</\1>|<.*? /> – simple HTML tag. ^\s*|\s*$ – leading/trailing whitespace. [1-9][0-9]{4,} – QQ number. [1-9]\d{5}(?!\d) – Chinese postal code. \d+\.\d+\.\d+\.\d+ – IPv4 address.

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

– IPv4 validation.

((?:(?:25[0-5]|2[0-4]\d|[01]?\d?\d)\.){7,7}[0-9a-fA-F]{1,4}|...)

– IPv6 validation (truncated for brevity).

^((?!0000)[0-9]{4}-(?:(?:0[1-9]|1[0-2])-(?:0[1-9]|1[0-9]|2[0-8])|...))$

– full date validation with leap‑year check. <!--(.*?)--> – HTML comment extraction. ^\s*[a-zA-Z\-]+\s*[:]{1}\s[a-zA-Z0-9\s.#]+[;]{1} – CSS property detection.