Regular Expressions 101

Save & Share

Flavor

  • PCRE2 (PHP >=7.3)
  • PCRE (PHP <7.3)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java 8
  • .NET 7.0 (C#)
  • Rust
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests (21)

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
An explanation of your regex will be automatically generated as you type.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression

/
/
i

Unit Tests

Valid: simple
Valid: very common
Valid: disposable email with symbol
Valid: with hyphen
Valid: fully qualified domain
Valid: with "+" (may go to user.name@example.com inbox depending on mail server)
Valid: One letter local part
Valid: strange example
Valid: local domain name with no TLD, although ICANN highly discourages dotless email addresses
Valid: see Wikipedia List of Internet top-level domains
Valid: space between quote
Valid: quoted double dot
Valid: bangified host route used for uucp mailers
Valid: % escaped mail route to user@example.com via example.org
Invalid: no @
Invalid: multiple @
Invalid: none of the special characters in this local-part are allowed outside quotation marks
Invalid: quoted strings must be dot separated or the only element making up the local-part
Invalid: spaces, quotes, and backslashes may only exist when within quoted strings and preceded by a backslash
Invalid: even if escaped (preceded by a backslash), spaces, quotes, and backslashes must still be contained by quotes
Invalid: local part is longer than 64 characters