Internet provider secretly limit the bandwidth

Question

I think my internet provider secretly limit my download speed. It has a webpage to test the upload and download speed, I tested the speed while downloading files.

I noticed that whenever I start testing, my file download speed would increase and reach the claimed bandwidth ~10Mb/s, but after the test is done, the file download speed would decrease to ~100Kb/s. I double checked, there is no other process than downloader and web browser that uses the internet.

I tried resend the OPTIONS and POST request but without success. I found a variable in a function ('MAXUPLOADSIZE') in the js code that might control the duration of the test but I don't know how to change the js code at runtime (Haven't tried Fiddler yet). Now I just use Selenium to simulate clicking on the test page.

Any idea on how to deal with this kind of problem? I don't know nothing about network/javascript stuff, any idea would be appreciated.

---

Updated solution:

I end up using speedtest-cli and writing a script to constantly test the upload speed, now my network speed is finally capped at the maximum bandwidth. I don't know why it works, this is very interesting.

Answer 1

It's something that's known to happen, and if it's on the ISP side, there's little you can do on your end. On the other hand, it's entirely possible that the source you're downloading from is slow, overloaded, or far away. Some ISPs have great speeds within their network or specific peers (my ISP, for example, has gigabit but their upstream to other countries can be limited).

Chances are messing with your settings will do nothing - especially if your ISP is being sneaky.

There are a few things worth trying. There are speed tests that use a range of different servers like this one by the battle for the net. Get a friend on another ISP or even in another country to see if the download speeds for those sites are just as bad.

Anecdotally some folks have reported better speeds through a VPN (although this is not always an option), or even running speed tests while downloading. If your ISP is dodgy, though, the best way to deal with it is to vote with your feet and wallet and switch ISPs.