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 single character of: a, b, c or d
    [[ab][cd]]
  • 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]
  • Character class intersection
    [\w&&[^\d]]
  • 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

"
"
g

Test String

Code Generator

Language

Generated Code

package main import ( "regexp" "fmt" ) func main() { var re = regexp.MustCompile(`\s(?=\w*[0-9])(?=\w*[A-Z])([A-Z\d]{11}|[A-Z\d]{7})\s`) var str = `From: Creedence Colossal <tmpwchange@gmail.com> To: "tmpwchange@gmail.com" N4EYN5DW9CT <tmpwchange@gmail.com> Subject: +14242767352 5/18/2021 9:22:23 PM Return-Path: <tmpwchange@gmail.com> Received: from [192.168.1.34] (047-232-149-032.res.spectrum.com. [47.232.149.32]) by smtp.gmail.com with ESMTPSA id x6sm4564717pfj.24.2021.05.18.21.22.51 for 9GS4C81 <tmpwchange@gmail.com> (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 May 2021 21:22:52 -0700 (PDT) Date: Tue, 18 May 2021 21:22:23 -0700 Message-Id: <U8F57JFLRDU4.QQL5G9PGZESZ2@DESKTOP-6PJ7AGK> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" 9GS4C84 -- This 8001355 email ESMTPSA has been checked for viruses by Avast antivirus software.` for i, match := range re.FindAllString(str, -1) { fmt.Println(match, "found at index", i) } }

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 Golang, please visit: https://golang.org/pkg/regexp/