I’ve built a simple reverse proxy and have confirmed that it is running well by configuring Windows and Linux systems to use it. I’ve also used ‘curl’ on OS X to confirm that it is working as it should.
I configured OS X El Capitan via System Preferences > Network > Proxies to use the proxy server, but it will not. Safari and latest versions of Chrome rely on system level proxy settings to use proxy services, so neither one will even attempt to connect to it.
Firefox on OS X does not use OS X system level proxy settings and can be configured to use the proxy. It works fine.
How do I get OS X to respect the settings?
Found the problem. When configuring system level proxy settings in OS X, you need to specify the domain name or IP address of the proxy without the protocol ‘http’ or ‘https’.