Regular Expressions 101

Save & Manage Regex

  • Current Version: 5
  • 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]
  • 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
Processing...

Test String

Code Generator

Generated Code

const regex = /(.+):(\d+):\s*(syntax\serror,\s)?(.+)/g; // Alternative syntax using RegExp constructor // const regex = new RegExp('(.+):(\\d+):\\s*(syntax\\serror,\\s)?(.+)', 'g') const str = `C:/Users/Landon/Desktop/bad.rb:2: syntax error, unexpected =>, expecting '}' 'key' => 'value', ^ C:/Users/Landon/Desktop/bad.rb:2: syntax error, unexpected ',', expecting '}' C:/Users/Landon/Desktop/bad.rb:3: syntax error, unexpected =>, expecting '}' 'other key' => 'value missing closing tick ^ C:/Users/Landon/Desktop/bad.rb:3: unterminated string meets end of file C:/Users/Landon/Desktop/bad.rb:3: can't find string "asdf" anywhere before EOF C:/Users/Landon/Desktop/bad.rb:3: unknown regexp optionwxyz - asdf C:/Users/Landon/Desktop/bad.rb:3: invalid multibyte char (asdf) C:/Users/Landon/Desktop/bad.rb:3: unterminated regexp meets end of file C:/Users/Landon/Desktop/bad.rb:3: unterminated here document identifier C:/Users/Landon/Desktop/bad.rb:3: incomplete character syntax C:/Users/Landon/Desktop/bad.rb:3: unterminated quoted string meets end of file C:/Users/Landon/Desktop/bad.rb:3: \`\$' without identifiers is not allowed as a global variable name C:/Users/Landon/Desktop/bad.rb:3: \`\$asdf' is not allowed as a global variable name C:/Users/Landon/Desktop/bad.rb:3: \`@' without identifiers is not allowed as an instance variable name C:/Users/Landon/Desktop/bad.rb:3: \`@@' without identifiers is not allowed as a class variable name C:/Users/Landon/Desktop/bad.rb:3: \`@asdf' is not allowed as an instance variable name C:/Users/Landon/Desktop/bad.rb:3: \`@@asdf' is not allowed as a class variable name C:/Users/Landon/Desktop/bad.rb:3: embedded document meets end of file C:/Users/Landon/Desktop/bad.rb:3: Invalid char \`\\\\x%02X' in expression C:/Users/Landon/Desktop/bad.rb:3: string literal encodings differ (asdf / wxyz) C:/Users/Landon/Desktop/bad.rb:3: identifier %"PRIsVALUE" is not valid to get C:/Users/Landon/Desktop/bad.rb:3: identifier asdf is not valid to get C:/Users/Landon/Desktop/bad.rb:3: identifier %"PRIsVALUE" is not valid to set C:/Users/Landon/Desktop/bad.rb:3: invalid local variable - asdf C:/Users/Landon/Desktop/bad.rb:3: both block arg and actual block given C:/Users/Landon/Desktop/bad.rb:3: Can't set variable \$asfd C:/Users/Landon/Desktop/bad.rb:3: block argument should not be given C:/Users/Landon/Desktop/bad.rb:3: regexp encoding option 'asdf' differs from source encoding 'wxyz'`; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }

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 JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions