Fiddler can be used as a proxy server with authentication. The following steps need to be followed to set proxy credentials in Fiddler.
Set Proxy host
The machine in which the fiddler is running will be the proxy host.
Set proxy port
Set username and password
generate base64 encoding of username password combination in the following formate. You may use TextWizard of fiddler to do the conversion.
where myUser is the username and myPasscode is password. The base64 encoded content for the above combination is bXlVc2VyOm15UGFzc2NvZGU=
Then type the following command in QuickExec command. Note that the last part in the command is the base64 encoded content prepared.
prefs set fiddler.proxy.creds bXlVc2VyOm15UGFzc2NvZGU=