Is my port open?
Set up a port forward for a game, console or server and not sure it works? This connects from the internet back to your connection on the port you pick and tells you whether anything answered.
What this can and can't test
It tests TCP. Many games also use UDP, which no website can test, because UDP doesn't answer unless the game itself is running and talking. For UDP, run the connection check to see your NAT type instead.
Privacy
The check only ever connects to the address you're visiting from, once per click. That address isn't stored or logged.
Forwarding ports rarely lowers lag on its own. If games feel slow, the one-click Boost finds where the lag starts.