官方版

Fiddler’s “Automatic Authentication” feature doesn’t work when server and client are on the same machine?

If IIS and the client are on the same machine, then a feature called “Loopback protection” is causing the authentication request to fail because your computer recognizes that it is authenticating to itself, and it is unexpected (due to the proxy).
You’ll need to set DisableLoopbackCheck=1 as described here: http://support.microsoft.com/kb/926642

谷歌翻译版

当服务器和客户端在同一台机器上时，Fiddler的“自动身份验证”功能无法工作?

如果IIS和客户端在同一台机器上，那么一个称为“环回保护”的特性将导致身份验证请求失败，因为您的计算机认识到它正在对自己进行身份验证，而这是意外的(由于代理)。
您需要按照此处的说明设置DisableLoopbackCheck = 1：http://support.microsoft.com/kb/926642 http://support.microsoft.com/kb/926642