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

Tools

Sponsors
There are currently no sponsors. Become a sponsor today!
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
No Match

/
/
gm

Test String

Code Generator

Language

Generated Code

using System; using System.Text.RegularExpressions; public class Example { public static void Main() { string pattern = @"^((?:https?|ftp|smtp):\/\/)?((?:[a-z0-9]+\.)*[a-z]+|(?:(?:25[0-5]|2[0-4]\d|1?\d{2}|\d)\.){3}(?:25[0-5]|2[0-4]\d|1?\d{2}|\d))(:\d+)?(\/.+\/?)*$"; string input = @"https://www.reddit.co.jp/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://www.reddit.com/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://old.reddit.com/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://reddit.co.jp/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://reddit.com/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://localhost/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://127.0.0.1/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://127.0.0.1:3000/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://localhost:3000/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://reddit.com:3000/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://new.reddit.com:3000/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://420.reddit.com:3000/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ ftp://ftp.mitsu.xd:6969/secret-linux-isos smtp://69.420.com/does-smtp-even-supports-paths?idk=pls%20help https://pbs.twimg.com/media/FXiW8wAXwAAqKe3.jpg?name=orig # Don't match these: https://foo#bad.com/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://.../r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://1024.0.0.7/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://360.0.0.7/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ https://127.w.0.1/r/ProgrammerHumor/comments/vxhbku/a_regex_god/ "; RegexOptions options = RegexOptions.Multiline; foreach (Match m in Regex.Matches(input, pattern, options)) { Console.WriteLine("'{0}' found at index {1}.", m.Value, m.Index); } } }

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 C#, please visit: https://msdn.microsoft.com/en-us/library/system.text.regularexpressions.regex(v=vs.110).aspx