The free web debugging proxy
for any browser, system or platform



Key Features

Web Debugging

Debug traffic from PC, Mac or Linux systems and mobile devices. Ensure the proper cookies, headers and cache directives are transferred between the client and server. Supports any framework, including .NET, Java, Ruby, etc.

Performance Testing

Fiddler lets you see the “total page weight,” HTTP caching and compression at a glance. Isolate performance bottlenecks with rules like “Flag any uncompressed responses larger than 25kb.”

HTTP/HTTPS Traffic Recording

Fiddler is a free web debugging proxy which logs all HTTP(s) traffic between your computer and the Internet. Use it to debug traffic from virtually any application that supports a proxy like IE, Chrome, Safari, Firefox, Opera and more.

Web Session Manipulation

Easily manipulate and edit web sessions. All you need to do is set a breakpoint to pause the processing of the session and permit alteration of the request/response. You can also compose your own HTTP requests to run through Fiddler.

Security Testing

Use Fiddler for security testing your web applications -- decrypt HTTPS traffic, and display and modify requests using a man-in-the-middle decryption technique. Configure Fiddler to decrypt all traffic, or only specific sessions.

Customizing Fiddler

Benefit from a rich extensibility model, ranging from simple FiddlerScript to powerful Extensions which can be developed using any .NET language. 
See full list of ready-made add-ons.

Want Fiddler's Power in
Your .NET App?

FiddlerCore is the core proxy engine used by Fiddler to intercept and modify web traffic. You can integrate FiddlerCore into your .NET applications to provide unprecedented functionality.

More about FiddlerCore

Supported Technologies

Any Browser

Fiddler web debugging proxy helps you record, inspect and debug traffic from any browser.

Any System

Debug web traffic from any Windows-based PC, Mac or Linux system and mobile devices alike.

Any Platform

Fiddler is here to help, no matter what platform or language you use to develop.

Companion Tools

Fiddler and Geoedge

Debug traffic from any geo-location with Geoedge

Leverage Fiddler and the Geoedge global proxy network to monitor, inspect and debug traffic from over 130 locations. You can access Geoedge’s servers directly within the familiar Fiddler environment and easily switch from one location to another. With Geoedge you get access to:

  • High-performance servers - Fast, unmasked and secure access to web content
  • True geo-located IPs - Servers physically located all over the world
  • Unmatched reliability - 99.9% network uptime

More about Geoedge global proxy network



Integrate FiddlerCore into your application. FiddlerCore is the core proxy engine used by Fiddler to intercept and modify web traffic. You can integrate FiddlerCore into your .NET applications to provide unprecedented functionality.

More about FiddlerCore


Need to collect a web capture from an end-user and nervous about pointing them at the full version of Fiddler? Try FiddlerCap, a simple "VCR-like" recorder that generates SAZ captures you can open in Fiddler.

More about FiddlerCap

FiddlerScript Editor

The FiddlerScript Editor is a text editor that helps you edit script rules for Fiddler. It offers syntax highlighting and a class explorer to help you author scripts.

More about
FiddlerScript Editor

Related Products

Simulate Real User Load Using Fiddler Captures

Fiddler is an excellent tool for understanding the performance of your website, but how does your performance change when lots of users are hitting the site? Check out Telerik Test Studio powered by Fiddler to get an in-depth understanding of how your site performance degrades as the number of users increases.

Learn more
Test Studio and Fiddler

Try Open Source Framework for Building HTML5 Apps

Kendo UI Core is the open source version of Kendo UI, the comprehensive framework for building modern web and mobile apps with HTML5 and JavaScript. Kendo UI Core comes with 40+ widgets and framework features and it is licensed under the permissive Apache v2 license. The suite is suitable for commercial and open source projects.

Learn more
KendoUICore and Fiddler

Support and Learning

Eric Lawrence

About Eric Lawrence,
Fiddler and Telerik

In 2012, we added Fiddler to the Telerik product family. Even more exciting is that the creator of Fiddler, Eric Lawrence, came over from Microsoft to join the team. He's now delivering on his vision for Fiddler with the full backing of Telerik.

The Fiddler community is very important to us. We commit to keeping Fiddler free and expanding its value by further investing into the tool.

Next Steps

Download Fiddler Get Fiddler web debugger. It's free.
Ask the community Go to Fiddler forums to get help.
Simulate user load with Fiddler Test Studio load testing powered by Fiddler.