Using/Installing Fiddler on Mac OS


I could not find a good walkthrough so here is one for you.  Disclaimer:  This is on the latest OS and Latest version of Fiddler Beta


Install Mono – You can do this many ways but I wanted to do Xamarin development so I downloaded and installed Visual Studio for Mac and installed Mono as part of that installation:

Download Fiddler -

You did step 1 of the instructions on this page already if you installed Visual Studio.

Move the ‘fiddler-mac’ folder somewhere you have write access to.  I chose my Applications Folder.  Open in Finder:


and then just drag and drop it into Applications:


And here it is!


Next find the Terminal app in LaunchPad and run it:


Navigate to the Applications folder: cd /Applications/fiddler-mac/

Pre the instructions I ran this:  mono fiddler.exe

And got this error:

WARNING: The Carbon driver has not been ported to 64bits, and very few parts of Windows.Forms will work properly, or at all


  at <unknown> <0xffffffff>

  at (wrapper managed-to-native) System.Windows.Forms.XplatUICarbon.CGDisplayBounds (intptr) [0x00002] in <36fbc38531724d82b10aef6ebafea6e9>:0

And this error because I never ran/accepted the xcodebuild license :  Agreeing to the Xcode/iOS license requires admin privileges, please run “sudo xcodebuild -license” and then retry this command.

To fix this I first ran: sudo xcodebuild –license

and then used the correct 32 bit command to run mono and fiddler: mono --arch=32 fiddler.exe

You next have to allow changes to your networking so you will be prompted:


And Fiddler will start running!

When you start capture, again you need to enter your password to reset the proxy.


Pretty simple but like I said, I had no luck finding a good workaround and the fiddler instructions did not have the sudo xcodebuild –license, nor the mono --arch=32 fiddler.exe commands

Drop me a note if you found this useful!

Comments (1)

  1. sudo run it, or chown -R ug+w your Fiddler.exe files and subfolders should work as well. I think.. sans sudo, I kept seeing a settings.txt missing error when I left the app and returned to Terminal. With chmod, I no longer see the message (so assume it wrote OK).

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