Header Case Sensitivity Issue

[susantez]

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!

[Nick Iliev]

Hello Serkan Susantez,

 

It seems that Fiddler Everywhere is set to use HTTP/2, and in HTTP/2, the headers are automatically transferred to lowercase. As a result, the server is probably sending the headers as intended through HTTP 1.1 (where the lowercase is not mandatory). Then, the connection between Fiddler and your client application is probably in HTTP/2, where the mutation occurs.

Try to resolve the issue by explicitly disabling the HTTP/2 support in Fiddler Everywhere by unchecking the Settings > Connections > Enable HTTP/2 Support option.

 

Regards,
Nick Iliev
Progress Telerik

[susantez]

Thank you!