WireGuard: fast, modern, secure VPN tunnel
WireGuard is designed as a general purpose VPN for running on embedded interfaces and super computers alike, fit for many different circumstances. Initially released for the Linux kernel, it is now cross-platform (Windows, macOS, BSD, iOS, Android) and widely deployable.
WireGuard is originally open source and can be used for free, absolutely. There are many free VPNs that support WireGuard, and it is also included by default in the Linux kernel, so those who are adept at programming can establish these types of encrypted connections simply by typing in the command line.
WireGuard is generally considered one of the safest protocols today with its simple design, less code, and fewer possible bugs. This, coupled with its faster, state-of-the-art cryptography running within the Linux kernel, delivers a very easy-to-use VPN protocol that's tough to beat for speed, volume, and safety.
The main difference between WireGuard and OpenVPN is that WireGuard is much faster, while OpenVPN allows for higher privacy. Another important difference is that OpenVPN gives you a choice of encryption algorithm, whereas WireGuard forces you to use ChaCha20 for encryption and Poly1305 for authentication.