What is WireGuard and why does it matter?
WireGuard is the modern VPN protocol that has become the standard in recent years: significantly faster than older protocols like OpenVPN, built with far less code, and therefore less room for bugs. Pick WireGuard or a variant of it in your VPN app whenever it is offered.
A VPN protocol is the technique used to build the encrypted tunnel. For years, OpenVPN was the default: solid but heavy. WireGuard is the modern successor, built with a fraction of the code. Less code means a smaller attack surface, easier auditing, and in practice: noticeably higher speeds and faster connection times.
Virtually all major providers support WireGuard now. NordVPN built its own variant on top of it called NordLynx, Mullvad was one of its earliest large adopters, and Mozilla VPN runs on it entirely. ExpressVPN took its own route with Lightway, a similarly modern protocol it developed in-house.
For you as a user it is simple: if the app offers WireGuard, NordLynx, or Lightway, choose that. Older protocols like OpenVPN remain useful as a fallback on networks that block modern ones.