Internet speed drops dramatically while running any multiplayer game.

Jun 14, 2019
I have really weird problem with my internet. When I'm playing any multiplayer game that requires Internet connection my internet speed gets decreased dramatically.

My download speed is usually around 20 Mbps but when I launch any multiplayer game it gets decreased to 0.2 - 0.5 Mbps. I've tested it with league, csgo and overwatch - every game causes this problem. And it's funny because the game is running fine, normal ping, no lag, nothing - perfectly stable. It almost feels like when I connect to a game it disables all the Internet for everything else expect the game I'm playing which sounds ridiculus but that's what it actually feels like!

It started happening 3 days ago. I've noticed this problem when I was playing the game and listening to the music from youtube in the background and it started buffering really hard, even loading simple page in browser took like 10-20 seconds.
I've been searching on the Internet for 3 days trying to solve this issue but no luck.

This is my normal internet speed:

This is my speed when I'm running a game like CSGO (not even playing, just idling in the menu (???)):

I've also made some other download tests. Notice how my internet speed graph in task manager looks like:

The big pit of internet slowing down is when I was running CSGO, when I exited the game everything went back to normal.

This is the weirdest issue I've ever encountered. I think the call to my ISP may be the last thing I can do.
If anyone got any idea what's wrong I'd be really greatfull for the solution.