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

r"
"
s

Test String

Code Generator

Language

Generated Code

const regex = new RegExp('(?<=has been denied).*(401 to \\d{1,3}.\\d{1,3}.\\d{1,3}.\\d{1,3})', 's') const str = `2016-02-14 15:55:39.1094 Info HttpServer: HTTP Response 200 to 192.168.0.3. Time: 3ms. https://192.168.0.10:8920/emby/users/public 2016-02-14 15:55:43.8597 Info HttpServer: HTTP POST https://192.168.0.10:8920/emby/Users/authenticatebyname. UserAgent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:44.0) Gecko/20100101 Firefox/44.0 2016-02-14 15:55:43.8718 Info UserManager: Authentication request for <username> has been denied. 2016-02-14 15:55:43.8820 Error DtoUtils: ServiceBase<TRequest>::Service Exception *** Error Report *** Version: 3.0.5821.0 Command line: /usr/lib/emby-server/bin/MediaBrowser.Server.Mono.exe -programdata /var/lib/emby-server -restartpath /usr/lib/emby-server/restart.sh Operating system: Unix 3.19.0.25 Processor count: 8 64-Bit OS: True 64-Bit Process: True Program data path: /var/lib/emby-server Mono: 4.2.1 (Stable 4.2.1.102/6dd2d0d Thu Dec 3 04:04:55 UTC 2015) Application Path: /usr/lib/emby-server/bin/MediaBrowser.Server.Mono.exe Invalid user or password entered. MediaBrowser.Controller.Net.SecurityException at MediaBrowser.Server.Implementations.Session.SessionManager+<AuthenticateNewSession>c__asyncC.MoveNext () <0x41c76b00 + 0x0080b> in <filename unknown>:0 --- End of stack trace from previous location where exception was thrown --- at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () <0x7fa7314f36d0 + 0x00029> in <filename unknown>:0 at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess (System.Threading.Tasks.Task task) <0x7fa7314f16b0 + 0x000a7> in <filename unknown>:0 at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (System.Threading.Tasks.Task task) <0x7fa7314f1630 + 0x0006b> in <filename unknown>:0 at System.Runtime.CompilerServices.TaskAwaiter.ValidateEnd (System.Threading.Tasks.Task task) <0x7fa7314f15e0 + 0x0003a> in <filename unknown>:0 at System.Runtime.CompilerServices.ConfiguredTaskAwaitable\`1+ConfiguredTaskAwaiter[TResult].GetResult () <0x7fa7314f1d10 + 0x00017> in <filename unknown>:0 at MediaBrowser.Api.UserService+<Post>c__async1.MoveNext () <0x41c75ea0 + 0x00680> in <filename unknown>:0 2016-02-14 15:55:43.8849 Error HttpServer: Error processing request for /emby/Users/authenticatebyname *** Error Report *** Version: 3.0.5821.0 Command line: /usr/lib/emby-server/bin/MediaBrowser.Server.Mono.exe -programdata /var/lib/emby-server -restartpath /usr/lib/emby-server/restart.sh Operating system: Unix 3.19.0.25 Processor count: 8 64-Bit OS: True 64-Bit Process: True Program data path: /var/lib/emby-server Mono: 4.2.1 (Stable 4.2.1.102/6dd2d0d Thu Dec 3 04:04:55 UTC 2015) Application Path: /usr/lib/emby-server/bin/MediaBrowser.Server.Mono.exe Invalid user or password entered. ServiceStack.HttpError No Stack Trace Available 2016-02-14 15:55:43.8913 Info HttpServer: HTTP Response 401 to 192.168.0.3. Time: 32ms. https://192.168.0.10:8920/emby/Users/authenticatebyname `; // 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