Transparent mode misconfiguration

MITMproxy has been setup in transparent mode on Ubuntu 18.04 LTS box. Went through and performed the sysctl changes and NAT changes recommended. All seems normal as no error messages were returned by Linux.

MITMProxy was launched with the command: sudo mitmproxy -T --host -e

The app window opens and all seem ready to rock and roll. The mobile device is set up to reach the internet via the laptop running MITMproxy. The mobile device WiFi connection completes at which point I open the Chrome browser to visit ‘’ on the mobile device and almost immediately start seeing a series of messages on the proxy: CONNECT request Protocol error in client request: Mitmproxy received an absolute-form request
even though it is not running in regular mode. This usually represents a misconfiguration.

I have gone back through the procedure multiple times now provided in the DOC found at

The Chrome browser on the mobile device displays, “HttpException('Mitmproxy received an blah, blah, blah)” message which it dutifully displays with a 400 Bad Request error message.

Being a noobie I suspect it is something simple. Any guidance is appreciated.


PIP3 Installed version 2 of MITMproxy. Removed version 2 and then downloaded Version 4. Placed version 4 in new directory and ran using command line ./mitmproxy