This is generally harmless, but can cause performance problems if you’re using Cisco VPN Software or Roaming User Profiles in Windows. Issue #1 is that, because Fiddler generates one certificate for each HTTPS site you visit, your Windows Certificate store can be “polluted” with dozens or hundreds of Fiddler-generated end-entity certificates. makecert.exe does not generate certificates compatible with iOS/Android.makecert.exe “pollutes” the current user’s certificate store.There are three downsides to the makecert.exe tool: (Certificates can be seen by launching the CertMgr.msc utility). All generated certificates are stored in the Fiddler-running user’s Windows certificate storage area. On Windows, Fiddler defaults to using Microsoft’s makecert.exe command line utility to generate the root and end-entity certificates. Developers provide their own certificate-related logic by implementing the ICertificateProvider3 interface on an assembly specified by the preference, which defaults to 'certmaker.dll'. Certificate Generatorsįiddler uses a pluggable architecture for certificate generation. In order to do so, the proxy executes a man-in-the-middle attack against the secure traffic to achieve that, Fiddler must generate a root certificate and use that root certificate to generate multiple end-entity certificates, one for each HTTPS site which is being intercepted. By default, Fiddler intercepts insecure traffic (HTTP) but it can be configured to decrypt secure (HTTPS) traffic.

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