Note: Mono 3.10 was broken by Bug #23553 which prevents Fiddler from launching on Mac. Mac Note: The WinForms framework on Mac is almost unusably buggy. Your best bet is to run Fiddler inside a Linux or Windows Virtual Machine and point the Mac's proxy settings at that.
What Is Mono For Mac
Mac OS X 10.7 or later
Author / Product:
Mono Team / Mono for Mac
Mono Framework For Mac
After you get Mono installed, it’s probably a good idea to run a quick Hello World program to make sure everything is set up properly. That way you’ll know that your Mono for Mac is working before you try writing or running a more complex application. The Mono project focuses on compilers and runtime libraries and does not directly provide an IDE. Developers must choose from a series of available tools the one best suited for them. MonoDevelop is a Mono/C# Integrated Development Environment for Windows, Linux and macOS. It parses your C# and VB programs as you type them and is able to provide contextual completion of methods.
Pick an installation directory where you want your new copy of Mono to be installed. Let's call that location PREFIX. Your Mono installation and its dependencies will be installed there. For example, I like to use the directory /opt/mono, so I would replace PREFIX with /opt/mono in the following discussion.
If you have more than one Mono installation (for example to keep multiple versions around), you will want to read the document on Parallel Mono Environments on how to keep your various Mono installations separate.
Also Available: Download Mono for Windows