Since a VPN encrypts all your online traffic, any VPN will slow down your connection speed to some extent. With the best VPNs, however, the difference in speed will be unnoticeable. If you're using a top VPN and your connection seems slower than normal, you might be connected to an overcrowded server. This is not a problem - just disconnect and reconnect to a different server.
Many ISPs have been known to throttle, or slow down, your connection based on your online activity. When you use a VPN, your activity will be hidden from your ISP, and you can avoid throttling.
For ultra-fast speeds get ExpressVPN, which is the fastest VPN we tested, thanks to its advanced technology.