If you install Piwik, connecting through a reverse proxy (https-to-http), the following line should be automatically added to your config/config.ini.php file during the Piwik installation:
[General] assume_secure_protocol = 1
If you install Piwik from behind the reverse proxy (where Piwik can’t detect https will be used), you should set the above manually. Also, depending on your proxy server, the Visitor IP is set in a different HTTP Header which should also be automatically detected on install and added to your config/config.ini.php:
[General] ; CloudFlare proxy ; proxy_client_headers = HTTP_CF_CONNECTING_IP ; ISP proxy (Client-IP) ;proxy_client_headers = HTTP_CLIENT_IP ; standard proxy ;proxy_client_headers = HTTP_X_FORWARDED_FOR ;proxy_host_headers = HTTP_X_FORWARDED_HOST
If Piwik was unable to detect your proxy configuration, you may add these lines manually in your Piwik config.ini.php file (remove the leading “;” character to enable the setting).