While testing my mobile application using Fiddler as a system proxy, I am encountering an issue. Specifically, some HTTP response headers appear to be altered in terms of case sensitivity when they reach the application, which is causing functional discrepancies.

In the backend response, the headers are correct, as verified in Fiddler. However, when the same response reaches the mobile application, some headers are being received in lowercase, even though they are correctly capitalized in Fiddler.

For example, the header userToken  is received as userToken by the application. This discrepancy is illustrated in the attached screenshots:

• Screenshot 1 shows the correct header "userToken" as displayed in Fiddler.
• Screenshot 2 shows how the header "usertoken" appears in the Xcode logs of my mobile application.

Could you please advise on how to prevent Fiddler from altering the case of the headers or if there is a configuration setting that needs to be adjusted? Your assistance in resolving this issue would be greatly appreciated.

Thank you for your support!

I want to setup proxy for a c++ application for android.

Here is my setup:

When I turn on fiddler capture and go to a specific site, an http 503 error occurs.

It seems that fiddler has been blocked on that site.

Is there a way to capture this site?

https://smartstore.naver.com/j-flow

https://fpcy.hunan.chinatax.gov.cn:8083/NWebQuery/yzmQuery

This website support decryption under Windows 10 but does not support decryption under Windows 7.

version:v5.0.20244.10953 

This website has enabled TLS1.2 and TLS1.3.

The open-source tool mitmproxy supports decryption under Windows 7.

If I have the fiddler classic running and i try to debug my azure function .net 7  I get an error in the attachment.  I'm not using grpc in my function it literally is an endpoint that calls another Rest endpoint.  Is there any way that I can have fiddler running and a azure function in debug running at the same time

Okay.  I finally got a  fiddler everywhere license.   Now, I need help in getting this tool to work with visual studio 2022 and running an azure function locally from my machine.  When I start the fiddler everywhere, i see the traffic coming through including Http/2 traffic.  When I go run the visual studio 2022 and start my azure function I get this message:  Error starting gRPC call. HttpRequestException: Requesting HTTP version 2.0 with version policy RequestVersionOrHigher while unable to establish HTTP/2 connection.    Is there something I have to change in vs 2022 ?  As soon as I turn off fiddler everywhere the function works fine?

I would like to capture Fiddler traces of an agent communicating with the a cloud service through (I believe) certificates in the local machine store.

I believe the agent is implemented in .Net. I edited the machine.config file as described here, and Decrypt HTTPS traffic is enabled in Fiddler classic.

I believe I am seeing traffic in Fiddler. However, the agent is failing authentication with the cloud service due to an invalid certificate.

I see Fiddler creating its self-signed certificates in the local user store, but no certs are being created in the local machine store

Any pointers on how to do this will be greatly appreciated!

So I'm new to Fiddler, I'm using it on Linux via the AppImage download on Debian/Testing. I'm trying to use it to debug something on my Android phone. When I seelect `Capture and Inspect Traffic` -> `Remote Devices` -> `Android`, click Next, select my ethernet interface, I try and go (on my phone or another machine) to the IP & Port that it shows, but can't connect. When I check the host machine's opened ports, it shows it opened up on IPv6, not IPv4, even though it's showing the IPv4 local address. I can ping the host IPv4 address just fine, but doesn't look like Fiddler is opening up a port on it.

$ netstat -anp  | grep -i 8866
tcp6       0      0 :::8866                 :::*                    LISTEN      230864/Fiddler.WebU 

Hello

Yesterday I installed Fiddler, to test it.

I sniff https request to instagram.
(using the filter  CONTAINS   instagram)

Then I tried to do it for my python code, running in terminal window of Ubuntu, on windows wsl.
Nothing appears in the requests and response.

Today I thought to try again and I open the Fiddler, but it sniff NOTHING.
(Even if I clear the filter)

Any hints to those two issues ?

Thanks