Ask HN: Internet magically gets faster when opening speedtest?

Yes, to a certain extent your ISP is watching to see if you run a speedtest and will open up more bandwidth to you in the event you do. However, if they were throttling you, which is not guaranteed, the most likely reason for throttling you is that the network hub for your neighborhood was under an heavy load, and they throttled everyone on your backbone hub to ensure that critical operations don't experience interruptions.

What you might consider critical operations might not agree with what your ISP considers critical of course, but they're a for profit business rather than a utility. So, what you consider a valid reason for throttling you doesn't count for squat. The reason they sped you up is that despite the fact that they carefully crafted their service contract to say they legally can throttle you for any reason or no reason at all, it reduces the number of complaints calls they don't intend to do anything about.

It also gives them plausible deniablity, and weirdly enough a useful metric for identifying hardware problems. They can simply make you think that the problem was the individual web service you were connecting to, or maybe just all of cloud flare. But more than that, they are able to track the number of times in a day that people visited a speedtest site, and whether they were able to get your speed up to the expected level. This functions as an early warning sign that they need to increase the total available bandwidth in an area if those numbers become what your ISP considers unacceptable.

Again, what your ISP considers unacceptable and what you consider unacceptable are not the same, but they're a for profit business rather than a regulated non-profit utility.

Instead, I wonder if your router or something else on your network stack is a little wonky. Do speeds increase when you reboot your router or cable modem? When you have slow speeds, does another device on the network also suffer slow speeds?