As I understand it they're ultimately just doing traffic shaping. If the edge of their network thinks you're downloading a video stream they'll throttle the th

As I understand it they're ultimately just doing traffic shaping. If the edge of their network thinks you're downloading a video stream they'll throttle the throughput to ~3.5Mbps. This is approximately equivalent to a 480p stream, so intelligent streaming apps (e.g: Netflix, YouTube, et al.) will notice this and downgrade the quality to avoid buffer stalls. On their new plan "T-Mobile One" this behavior is always on unless you opt out by purchasing an "HD Day Pass." (They upsell you on an add-on that gives you "free HD Day Passes" but you still have to activate them every day.) On their previous plan "Simple Choice" the network behaves essentially the same, but it was behind a toggle called on your billing profile called "BingeON" whereby if it was shaping your traffic it would zero-rate it on your bill. --- One thing I'm not sure about is how they do traffic shaping in the face of transmitting the stream over HTTPS/TLS, perhaps it's just a whitelist of IPs for known services? (I know businesses get away with shaping/monitoring TLS traffic by using MITM proxies on the edge of the network; but that assumes control of the certificate truststore on your network's endpoints, which T-Mobile doesn't have.)