Mastering Regex: Essential Patterns for Numbers, Text, and Special Formats

Number Validation Expressions

Digits: ^[0-9]*$ Exactly n digits: ^\d{n}$ At least n digits: ^\d{n,}$ m‑n digits: ^\d{m,n}$ Zero or non‑zero leading numbers: ^(0|[1-9][0-9]*)$ Non‑zero leading number with up to two decimal places: ^([1-9][0-9]*)+(.[0-9]{1,2})?$ Positive or negative number with optional 1‑2 decimal places: ^(\-)?\d+(\.\d{1,2})?$ Signed integer or decimal: ^(\-|\+)?\d+(\.\d+)?$ Positive real number with 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"*$ or ^-[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‑point number: ^\d+(\.\d+)?$ or ^[1-9]\d*\.\d*|0\.\d*[1-9]\d*|0?\.0+|0$ Non‑positive floating‑point number: ^((‑\d+(\.\d+)?)|(0+(\.0+)?))$ or ^(-([1-9]\d*\.\d*|0\.\d*[1-9]\d*))|0?\.0+|0$ 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]*)))$

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

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

Character Validation Expressions

Chinese characters: ^[\u4e00-\u9fa5]{0,}$ Alphanumeric (4‑40 chars): ^[A-Za-z0-9]+$ or ^[A-Za-z0-9]{4,40}$ Any characters, length 3‑20: ^.{3,20}$ Only letters: ^[A-Za-z]+$ Only uppercase letters: ^[A-Z]+$ Only lowercase letters: ^[a-z]+$ Alphanumeric only: ^[A-Za-z0-9]+$ Alphanumeric or 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}$ Allow specific symbols (%&',;=?$): [^%&',;=?$\x22]+ Disallow tilde (~):

[^~\x22]+

Other Useful Patterns

Match any character except newline: .* Match Chinese characters: /[\u4E00-\u9FA5]/ Match full‑width symbols:

/[\uFF00-\uFFFF]/

Special‑Purpose 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 (China): ^(13[0-9]|14[5|7]|15[0-9]|18[0-9])\d{8}$ Phone number (various formats): ^(\(\d{3,4}-)|\d{3.4}-)?\d{7,8}$ Domestic phone (e.g., 0511-4405222): \d{3}-\d{8}|\d{4}-\d{7} Identity card (15 or 18 digits): ^\d{15}|\d{18}$ Short ID (digits, optional trailing x): ^([0-9]){7,18}(x|X)?$ or ^\d{8,18}|[0-9x]{8,18}|[0-9X]{8,18}?$ Username (letter start, 5‑16 chars, letters/digits/underscore): ^[a-zA-Z][a-zA-Z0-9_]{4,15}$ Password (letter start, 6‑18 chars, letters/digits/underscore): ^[a-zA-Z]\w{5,17}$ Strong password (8‑10 chars, must include upper, lower, digit): ^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,10}$ Date (yyyy‑mm‑dd, leap‑year aware):

^((?!0000)[0-9]{4}-(?:(?:0[1-9]|1[0-2])-(?:0[1-9]|1[0-9]|2[0-8])|(?:0[13-9]|1[0-2])-(?:29|30)|(?:0[13578]|1[02])-31)|(?:[0-9]{2}(?:0[48]|[2468][048]|[13579][26])|(?:0[48]|[2468][048]|[13579][26])00)-02-29)$

Month (01‑12): ^(0?[1-9]|1[0-2])$ Day of month (01‑31): ^((0?[1-9])|((1|2)[0-9])|30|31)$ Money formats (various): ^[1-9][0-9]*$, ^(0|[1-9][0-9]*)$, ^(0|-?[1-9][0-9]*)$, ^[0-9]+(.[0-9]+)?$, ^[0-9]+(.[0-9]{2})?$, ^[0-9]+(.[0-9]{1,2})?$, ^[0-9]{1,3}(,[0-9]{3})*(.[0-9]{1,2})?$, ^([0-9]+|[0-9]{1,3}(,[0-9]{3})*)(.[0-9]{1,2})?$ 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: \n\s*\r HTML tag: <(\S*?)[^>]*>.*?</\1>|<.*? /> Trim leading/trailing whitespace: ^\s*|\s*$ or (^\s*)|(\s*$) QQ number: [1-9][0-9]{4,} Chinese postal code: [1-9]\d{5}(?!\d) IPv4 address: \d+\.\d+\.\d+\.\d+ IPv4 (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))

Extract comments: <!--(.*?)--> Find CSS property: ^\s*[a-zA-Z\-]+\s*[:]{1}\s[a-zA-Z0-9\s.#]+[;]{1} Extract page hyperlinks:

(<a\s*(?!.*\brel=)[^>]*)(href="https?:\/\/)((?!(?:(?:www\.)?'.implode('|(?:www\.)?', $follow_list).'))[^" rel="external nofollow" ]+)")

Extract page images: \\< *[img][^\\>]*[src] *= *[\"\']{0,1}([^\"\'\ >]*) Extract color codes: ^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$ File extension validation (txt): ^([a-zA-Z]\:|\\)\\([^\\]+\\)*[^\/:*?"<>|]+\.txt(l)?$ IE version detection:

^.*MSIE [5-8](?:\.[0-9]+)?(?!.*Trident\/[5-9]\.0).*$

References

https://www.runoob.com/regexp/regexp-tutorial.html

Online regex tester: http://tool.oschina.net/regex/

Note: The final result can use + or * as alternatives; remember to remove the escaping backslash when using the function.