OpenVPN is a VPN protocol. A VPN protocol, or a “tunneling protocol,” is the set of instructions your device uses to negotiate the secure encrypted connection that forms the network between your computer and another.
OpenVPN uses SSL/TLS to handle its key exchange, has no known vulnerabilities, supports Perfect Forward Secrecy, and is very stable. It also supports both UDP and TCP.
OpenVPN is widely considered to be one of the most secure VPN software solutions. It is also open-source, which means that anyone can verify its code or use it for free. You can read more about how OpenVPN compares to other VPN protocols on our blog post, Which VPN protocol is the best?
The ProtonVPN Windows application and the Linux command line tool use OpenVPN to create the encrypted VPN tunnel and keep your Internet activity private and secure. If you are having connection trouble, visit this page to see how you can change from UDP to TCP.