Speedtest is a more accurate measure of what you're actually paying for - which is a connection to the ATT network. The speedtest server is right on their netwo

Speedtest is a more accurate measure of what you're actually paying for - which is a connection to the ATT network. The speedtest server is right on their network most likely. Fast.com is a more functional test, specifically measuring how fast a connection on the ATT network in that area to the Netflix servers is. You're not paying ATT for a 24mb/s connection to every server on the entire internet because that would be impossible (how could your ISP promise you that much bandwidth across a transatlantic cable, or over a satellite link, or to a server connected via dialup). More generally, you're testing the strength of their peering and the route available for a specific purpose (watching Netflix). They aren't measuring the same thing at all. It would be like buying a 100mb/s router, plugging it into 20mb/s internet and then complaining that your router is broken because you can't download at 100mb/s. Your router will still show your ability to contact other computers in your house as 100mb/s (analogous to speedtest), but reaching computers outside your network (analogous to fast) is limited by the speed of your connection to the next larger network.