Regular Expressions 101

Save & Manage Regex

  • Current Version: 1
  • Save & Share
  • Community Library

Flavor

  • PCRE2 (PHP)
  • ECMAScript (JavaScript)
  • Python
  • Golang
  • Java
  • .NET 7.0 (C#)
  • Rust
  • PCRE (Legacy)
  • Regex Flavor Guide

Function

  • Match
  • Substitution
  • List
  • Unit Tests
Sponsors
An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • 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
Processing...

Test String

Code Generator

Language

Generated Code

import re regex = re.compile(r"(?im)^(?=.{1,64}@)(?:(\"[^\"\\]*(?:\\.[^\"\\]*)*\"@)|((?:[0-9a-z](?:\.(?!\.)|[-!#\$%&'\*\+\/=\?\^`\{\}\|~\w])*)?[0-9a-z]@))(?=.{1,255}$)(?:(\[(?:\d{1,3}\.){3}\d{1,3}\])|((?:(?=.{1,63}\.)[0-9a-z][-\w]*[0-9a-z]*\.)+[a-z0-9][\-a-z0-9]{0,22}[a-z0-9])|((?=.{1,63}$)[0-9a-z][-\w]*))$") test_str = ("// Mix valid/invalid\n\n" "david.jones@proseware.com\n" "d.j@server1.proseware.com\n" "jones@ms1.proseware.com\n" "j.@server1.proseware.com\n" "j@proseware.com9\n" "js#internal@proseware.com\n" "j_9@[129.126.118.1]\n" "j..s@proseware.com\n" "js*@proseware.com\n" "js@proseware..com\n" "js@proseware.com9\n" "j.s@server1.proseware.com\n" "\"j\\\"s\\\"\"@proseware.com\n" "js@contoso.中国.com\n\n" "=========================================\n\n" "// Valid\n\n" "simple@example.com\n" "very.common@example.com\n" "disposable.style.email.with+symbol@example.com\n" "other.email-with-hyphen@example.com\n" "fully-qualified-domain@example.com\n" "user.name+tag+sorting@example.com\n" "fully-qualified-domain@example.com\n" "x@example.com\n" "carlosd'intino@arnet.com.ar\n" "example-indeed@strange-example.com\n" "admin@mailserver1\n" "example@s.example\n" "\" \"@example.org\n" "\"john..doe\"@example.org\n\n" "// Invalid\n\n" "Abc.example.com\n" "A@b@c@example.com\n" "a\\\"b(c)d,e:f;g<h>i[j\\\\k]l@example.com\n" "just\\\"not\\\"right@example.com\n" "this is\\\"not\\\\allowed@example.com\n" "this\\\\ still\\\"not\\\\allowed@example.com\n" "1234567890123456789012345678901234567890123456789012345678901234+x@example.com\n" "john..doe@example.com\n" "john.doe@example..com\n") matches = regex.finditer(test_str) for match_num, match in enumerate(matches, start=1): print(f"Match {match_num} was found at {match.start()}-{match.end()}: {match.group()}") for group_num, group in enumerate(match.groups(), start=1): print(f"Group {group_num} found at {match.start(group_num)}-{match.end(group_num)}: {group}")

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Python, please visit: https://docs.python.org/3/library/re.html