Why does using a VPN usually slow down an internet connection?

Answer: Traffic travels farther to a VPN server before reaching the website, adding network delay.

Websites detect the VPN server and deliberately send data through a slower queue. — Wrong. A website can see the address of the VPN server, but ordinary slowdown is not caused by sites deliberately putting VPN traffic in a slower queue. The delay begins on the VPN path: encryption, a distant server, and an extra relay point. A busy VPN server can make a site feel throttled even when the site is not throttling.

Traffic travels farther to a VPN server before reaching the website, adding network delay. ✓ — Correct. Without a VPN, traffic goes from your device to the website; with one, it goes device to VPN server to website and back. That longer route adds distance and an extra relay point, raising latency and sometimes lowering throughput. Encryption adds processing overhead too, and a nearby, uncrowded server keeps the cost smaller.

Encryption overhead uses most of the connection's capacity, leaving little for downloads. — Wrong. Encryption and decryption do add processing work and some protocol overhead, which can raise latency. But that overhead normally takes a small share of capacity, not most of it, and it does not reserve bandwidth for the tunnel. The larger usual cost is the longer route through the VPN server.