Useful Regular Expressions for Developers

A regular expression, or regex, is a sequence of characters that specifies a match pattern in text. Often times regex is used for form validations and string-searching algorithms. Here are a few regex that are handy for developers:


  • Domain: ^([a-z][a-z0-9-]+(\.|-*\.))+[a-z]{2,6}$
  • Email: ^[_]*([a-z0-9]+(\.|_*)?)+@([a-z][a-z0-9-]+(\.|-*\.))+[a-z]{2,6}$
  • Letters only: ^[a-zA-Z]+$


  • Numbers only: ^[0-9]*$
  • Positive numbers: ^\d*\.?\d+$
  • Negative numbers: ^-\d*\.?\d+$
  • Numbers with spaces and parenthesis: /^(?:\+\d{1,3}|0\d{1,3}|00\d{1,2})?(?:\s?\(\d+\))?(?:[-\/\s.]|\d)+$/
  • Phone number: ^\+?[\d\s]{3,}$
  • Phone number with code: ^\+?[\d\s]+\(?[\d\s]{10,}$

Useful for Inputs

  • Letter and numbers only: ^[A-Z0-9]+$
  • Match blank input: ^\s\t*$
  • Match no input: ^$
  • Match new line: [\r\n]|$
  • Match URL: ^http\:\/\/[a-zA-Z0-9.-]+\.[a-zA-Z]{2,3}$
  • Match white space: ^\s+$
  • Match multiple white space: ^.\s{2,}.$

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