Regular Expressions 101

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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

/
/

Test String

Code Generator

Language

Generated Code

const regex = /(?:^(?:[A-Za-z0-9+\/]{4}\n?)*(?:[A-Za-z0-9+\/]{2}==|[A-Za-z0-9+\/]{3}=)$)/; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?:^(?:[A-Za-z0-9+\\\/]{4}\\n?)*(?:[A-Za-z0-9+\\\/]{2}==|[A-Za-z0-9+\\\/]{3}=)$)', '') const str = `hQGkA8uYb/u24XuEAQzAh5dH2QUPv5rQ+uHwVQQShCgmgJzlOAq+L6Ld4l4P0MOeUYK7Zvt7HiYM MzH5Pdi+VfiW0JWDqTdvQZS6o0SfBzoZqwqplAofLH+7hlu8qS0n6FFxXk2b4N5InMf/zWlqpDb6 oeGZQBbLJy69drKzpJYvqMM+OuzLUA4Wwv/WfwGtHo/fQ3H2JSFwPJz3QHuqvTrnIhO23fZa8Qpd M36LBbX3yqrmrJo63NHy9QL9eF6+/WU7qsKOxGSm2QlDaREKx6ZlXgZ+FY7SEt1C6PHPXhggf4Ts EF5rb+0goEniDbgiofYpUt0+aLkwsNnMYHx0+yAelPP45ZbCKxQe1Tk3gq5oAspWvUAvt6SqmNW5 CrakBXYSIpNqHWdjdW75yeUYPKIi1X1SZi1mVGy0ayrOGoPbOY6C77JwGMxqEOZtDLBiy/u9g1II Zy1dm3UxhX/Tir2Cg+5kTAVQ6qqliklhGSCcYw0rNMfl+q151zKu4/j9id5pHnrkjnjrV1odz3u/ aBKxLpzf8cf2BlYdRooqvFIbdJULftmn0lABukKc0eaPclSdz//DzTU318fpHnFbzlUpi82UVNL4 IUqUviQNw7SX41v90N39iNP3JmczkN8J70+o7NLYlcvp4xXIFOcRaDrinbCcXT1WfQ==`; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; if ((m = regex.exec(str)) !== null) { // 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