Social Security Numbers

This regular expression will validate social security numbers in a XXX-XX-XXXX format.

'/^([0-9]{3}[-]*[0-9]{2}[-]*[0-9]{4})*$/'


All Major Credit Cards

This regular expression will validate all major credit cards: American Express (Amex), Discover, Mastercard, and Visa.

1. //All major credit cards regex

2. '/^(?:4[0-9]{12}(?:[0-9]{3})?|5[1-5][0-9]{14}|6011[0-9]{12}|622((12[6-9]|1[3-9][0-9])|([2-8][0-9][0-9])|(9(([0-1][0-9])|(2[0-5]))))[0-9]{10}|64[4-9][0-9]{13}|65[0-9]{14}|3(?:0[0-5]|[68][0-9])[0-9]{11}|3[47][0-9]{13})*$/'


Alpha-Numeric Characters

Test for alpha-numeric characters with this regexp.

1. //Alpha-numeric characters only

2. '/^[a-zA-Z0-9]*$/'


Alpha-Numeric Characters With Spaces

Test for alpha-numeric characters and spaces with this regexp.

1. //Alpha-numeric characters with spaces only

2. '/^[a-zA-Z0-9 ]*$/'


Alphabetic Characters

This regex will test for alphabetic characters only (upper and lowercase).

1. //Alphabetic characters only

2. '/^[a-zA-Z]*$/'


American Express Credit Card

Verify Amex credit cards with this regexp.

1. //Amex credit card regex

2. '/^(3[47][0-9]{13})*$/'


Australian Postal Codes

If you need to verify Australian Postal Codes, use this regular expression.

1. //Australian Postal Codes

2. '/^((0[289][0-9]{2})|([1345689][0-9]{3})|(2[0-8][0-9]{2})|(290[0-9])|(291[0-4])|(7[0-4][0-9]{2})|(7[8-9][0-9]{2}))*$/'


Canadian Postal Codes

Tests for valid Canadian Postal Codes.

1. //Canadian Postal Codes

2. '/^([ABCEGHJKLMNPRSTVXY][0-9][A-Z] [0-9][A-Z][0-9])*$/'


Canadian Provinces

Evaluate Canadian province abbreviations with this regular expression.

1. //Canadian Province Abbreviations

2. '/^(?:AB|BC|MB|N[BLTSU]|ON|PE|QC|SK|YT)*$/'


Date (MM/DD/YYYY)

Validate the calendar date in MM/DD/YYYY format with this regex. Optional separators are spaces, hyphens, forward slashes, and periods. The year is limited between 1900 and 2099.

1. //Date (MM/DD/YYYY)

2. '/^((0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])[- /.](19|20)?[0-9]{2})*$/'


Date (YYYY/MM/DD)

Validate the calendar date in YYYY/MM/DD format with this regex. Optional separators are spaces, hyphens, forward slashes, and periods. The year is limited between 1900 and 2099.

1. //Date (YYYY/MM/DD)

2. '#^((19|20)?[0-9]{2}[- /.](0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01]))*$#'


Digits

This regex will test for digits (whole numbers).

1. //Digits only

2. '/^[0-9]*$/'


Diner's Club Credit Card

Test and verify Diner's Club credit card numbers with this regexp.

1. //Diner's Club credit card regex

2. '/^(3(?:0[0-5]|[68][0-9])[0-9]{11})*$/'


Emails

This email regex is not fully RFC5322-compliant, but it will validate most common email address formats correctly.

1. //Email regex

2. '/^([a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,4})*$/'


IP Addresses

Test IP Addresses with this regular expression.

1. //IP address regex

2. '/^((?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?))*$/'


Lowercase Alphabetic Characters

This regex will test for lowercase letters.

1. //Lowercase letters only

2. '/^([a-z])*$/'


MasterCard Credit Card

Verify MasterCard credit card numbers with this regex.

1. //MasterCard credit card numbers

2. '/^(5[1-5][0-9]{14})*$/'

Phone Numbers (North American)

This regex will validate a 10-digit North American telephone number with dashes.

1. //Phone number regex with dashes required

2. ^\d{3}-\d{3}-\d{4}$

Social Security Numbers

If you need to validate US Social Security Numbers, use this regular expression

1. //SSN regex

2. '/^([0-9]{3}[-]*[0-9]{2}[-]*[0-9]{4})*$/'

UK Postal Codes

This regexp verifies UK Postal Codes.

1. //UK Postal Codes regex

2. '/^([A-Z]{1,2}[0-9][A-Z0-9]? [0-9][ABD-HJLNP-UW-Z]{2})*$/'

Uppercase Alphabetic Characters

This regex will test for uppercase letters.

1. //Uppercase letters only

2. '/^([A-Z])*$/'

URLs

This URL regex will validate most common URL formats correctly.

1. //URL regex

2. '/^(((http|https|ftp):\/\/)?([[a-zA-Z0-9]\-\.])+(\.)([[a-zA-Z0-9]]){2,4}([[a-zA-Z0-9]\/+=%&_\.~?\-]*))*$/'

US States

Validate all 2-letter US State abbreviates with this regular expression.

1. //US States regex

2. '/^(?:A[KLRZ]|C[AOT]|D[CE]|FL|GA|HI|I[ADLN]|K[SY]|LA|M[ADEINOST]|N[CDEHJMVY]|O[HKR]|PA|RI|S[CD]|T[NX]|UT|V[AT]|W[AIVY])*$/'

US ZIP Codes

This regexp verifies US ZIP Codes, with an optional 4 number ZIP code extension.

1. //US ZIP Codes regex

2. '/^([0-9]{5}(?:-[0-9]{4})?)*$/'

Visa Credit Card

Verify Visa credit card numbers with this regex.

1. //Visa credit card numbers

2. '/^(4[0-9]{12}(?:[0-9]{3})?)*$/'



Here are some Regex Tutorials:
While this page doesn't go in depth on how to learn regular expressions, I will point you to some tutorials so that if you need to modify any of the above regexes or create your own, you'll be able to do so.

Regex Resources And Reference Sheets
There are a number of different regex cheat sheets, libraries, testers, and other resources around the web. Here are just a few of them.