Regular Expressions 101

Save & Manage Regex

  • Current Version: 17
  • 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

Substitution
Processing...

Code Generator

Language

Generated Code

const regex = /(?:^(?:[(]?\b(?:_xTagsx_)\b(?:and|[ ,.&+/-])*)+[:. \)-]*|(?:[:. \(-]|in|with|using)*(?:\b(?:_xTagsx_)\b(?:and|[ ,&+/)-])*)+([?.! ]*)$)/gim; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?:^(?:[(]?\\b(?:_xTagsx_)\\b(?:and|[ ,.&+\/-])*)+[:. \\)-]*|(?:[:. \\(-]|in|with|using)*(?:\\b(?:_xTagsx_)\\b(?:and|[ ,&+\/)-])*)+([?.! ]*)$)', 'gim') const str = `Note use of _xTagsx_ placeholder; this is replaced in code. Be careful: any escaped characters will require double-escape in string to form regexp. ** Flags should be gi in production; 'm' for test here only. Remove leading tags from: _xTagsx_ & _xTagsx_: Rest of title _xTagsx_ - _xTagsx_ - _xTagsx_ - Rest of title _xTagsx_ Rest of title _xTagsx_, _xTagsx_ & _xTagsx_ Rest of title _xTagsx_. Checking if string contains text from an array of substrings. _xTagsx_ and _xTagsx_: _xTagsx_ - Rest of title _xTagsx_/_xTagsx_ - Rest of title (_xTagsx_) Rest of title Remove Trailing tags (but leave final punctuation, if any) from: How to use <= in _xTagsx_ _xTagsx_? Rest of title (_xTagsx_) Rest of title (_xTagsx_/_xTagsx_ - _xTagsx_) Rest of title - in _xTagsx_. Leave alone: Use of _xTagsx_ in general. _xTagsx_as part of a word_xTagsx_`; const subst = `$1`; // The substituted value will be contained in the result variable const result = str.replace(regex, subst); console.log('Substitution result: ', result);

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