Google Chrome: Blocking Data Saver Proxy
Google Chrome's Data Saver feature is a proxy, performing on-the-fly optimizations, with the goal of reducing bandwidth usage and loading content for mobile devices faster. This is especially useful for cellular 3g/4g/LTE connections, due to the cost and speed of bandwidth.
According to Google's documentation, this feature is enabled by default on all Android devices, but in our experience, this is not always the case and depends on the Android version, device, and Google Chrome version. There is also a Chrome plugin for desktop operating systems.
With Data Saver enabled, DNS requests go directly through the proxy, bypassing DNSFilter enforcement.
To block Chrome's Data Saver proxy, which effectively allows circumventing any DNSFilter policies, simply block Proxy and Filter Avoidance in the Threats tab when editing a policy.
Alternatively, add only googlezip.net and datasaver.googleapis.com to your blacklist.