If you try to launch two instances of Fiddler/FiddlerViewer at the same time, you hit a sharing violation.

This file needs to be read with the correct sharing flags set.

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Loading custom MIME mappings failed
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Fiddler has encountered an unexpected problem. If you believe this is a bug in Fiddler, please copy this message by hitting CTRL+C, and submit a bug report at http://www.telerik.com/forums/fiddler.

The process cannot access the file 'C:\Users\ericlaw\Documents\Fiddler2\CustomMimeMappings.xml' because it is being used by another process.

Type: System.IO.IOException
Source: mscorlib
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)

   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)

   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options, String msgPath, Boolean bFromProxy)

   at System.IO.FileStream..ctor(String path, FileMode mode)

   at Fiddler.XmlFileMimeMappings..ctor(String filePath) in C:\Jenkins\Fiddler_Windows\workspace\FiddlerCore\FiddlerCore.Shared\Common\Core\MimeMapping\XmlFileMimeMappings.cs:line 38

   at Fiddler.frmViewer.š(Object , EventArgs ) in C:\Jenkins\Fiddler_Windows\workspace\Fiddler2\Fiddler.Shared\Viewer.cs:line 9968


Fiddler v5.0.20202.18177 (x64 AMD64) [.NET 4.0.30319.42000 on Microsoft Windows NT 10.0.19043.0] 
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OK   
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