Firefox's HTTP basic authentication dialog is encoding non-english user name and passwords incorrectly. Everything works when I enter English user name and password. However, if I input valid user name and/or password with non-english character(s) in them, I cannot login. The authentication fails. I turned to Fiddler and found that FireFox is sending incorrectly encoded Authorization header. Traces below. If I send correctly encoded Authorization header everything works. The test below uses Chinese characters. Working scenario using English user name and password: ------------------ GET http://myhost:8080/notification/syndication HTTP/1.1 Accept-Language: en-US User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E) Accept-Encoding: gzip, deflate Connection: Keep-Alive Authorization: Basic dXNlcjE6cGFzc3dvcmQ= Host: myhost:8080 Non-working scenario using non-English character user name and password: --------------- GET http://myhost:8080/notification/syndication HTTP/1.1 Accept-Language: en-US User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 6.1; WOW64; Trident/7.0; SLCC2; .NET CLR 2.0.50727; .NET CLR 3.5.30729; .NET CLR 3.0.30729; Media Center PC 6.0; .NET4.0C; .NET4.0E) Accept-Encoding: gzip, deflate Connection: Keep-Alive Authorization: Basic e1UNOnNwc3M= Host: myhost:8080 Note the incorrect Authorization header string product by Firefox code: Authorization: Basic e1UNOnNwc3M= Correct base64 encoding would have yielded this authorization header instead: Authorization: Basic 55m75b2V5ZCNOnNwc3M= Is this a bug in Firefox? Perhaps there is a configuration change that I need to make to input non-English user name and password in the basic authentication dialog? Chrome does not have this issue. Internet Explorer has the same problem.