Introducing flexible FiddlerCore licensing options. Read blog post


The power of Fiddler in your app


What is FiddlerCore

FiddlerCore is a .NET Class library you can integrate into your .NET Framework and Mono Framework applications. FiddlerCore allows you to capture and modify HTTP and HTTPS traffic just like Fiddler, without any of the Fiddler UI.

Why FiddlerCore

  • Battle-tested code used by millions of users of the Fiddler application.
  • Flexible licensing schemes for internal and public distribution.
  • Ongoing support from the core development team.

Key Features

  • HTTP and HTTPS traffic capture and modification.
  • Powerful object model for content filtering and modification.
  • Store and reload web traffic.
  • Support for virtually any client application.
  • Support for most devices via mobile proxy settings.

FiddlerCore for .NET

The install package contains .NET 2.0, 3.5, & 4.0 versions.


FiddlerCore for Mono Framework

A FiddlerCore.dll compiled targeting the Mono Framework is now in Alpha.


FiddlerCore Documentation

All FiddlerCore-related classes in C#, VB.NET and Managed C++ syntax.

Matt Heller
Founder and Chairman, Browsium

Browsium embraced FiddlerCore to build powerful browser management solutions. With hundreds of thousands of Browsium client installations worldwide, it has proven to be stable, reliable and efficient under a broad range of use and load scenarios. The Fiddler team is incredibly responsive, addressing issues and incorporating a solution that becomes a mainstream supported feature. Our teams also use Fiddler in customer application troubleshooting and creating customer configurations for their Browsium products.

Next Steps

Download FiddlerCore

Get FiddlerCore .NET Debugger.

Licensing Information

See commercial licensing options.

More about Fiddler

Get Fiddler web debugger. It's free.