While Ookla's Speedtest® helps testing Internet Access speeds, Fast.com (Netflix's own speed test service) is meant to provide a better end-to-end representation of video streaming content delivery across the Internet.
Netflix has its own speed test platform, hosted at fast.com, which uses Netflix servers to provide ISP-independent end-to-end performance testing. Netflix's speed test differs from other speed test sites because it uses Netflix's actual content delivery system (Open Connect) instead of testing against random servers, some of which are strategically placed by ISPs at the edge of the service providers' access network, for better results.
You may still use Ookla Speedtest® Powered V-TEST to test the Internet Access Speeds for the subscriber's service, to get an idea of what the typical upload and download throughputs are attainable on an Internet access link. However, this commonly used test is performed against the closest Ookla server (the one with the shortest round-trip delay), but it may not include transit over the vast Internet, to fully resemble the performance against the nearest Netflix content servers. Fast.com is meant to better represent the end-to-end video service delivery over any involved Core/Metro and Internet access networks.
On its website, Netflix publishes what seems to be a very conservative list of downstream throughputs (speeds) required for the different types of content resolutions (720p HD, 1080p FHD, and 4K UHD). However, image quality also depends on video compression levels and some other factors. Nonetheless, the fast.com method may be the most representative speed test for checking or troubleshooting issues related to Netflix streaming services.
Refer to the section below for a list of VeEX products supporting hardware-based Fast.com speed testing.