OpenVPN is a free, open-source virtual private network (VPN) application that encrypts all data travelling between your device and a VPN server you choose. It uses established encryption protocols to protect your internet activity from being monitored by your internet service provider, public WiFi operators, or other parties on the network.
The software works on Windows, macOS, Linux, iOS, and Android. Because the code is publicly available, security researchers regularly audit it for vulnerabilities. OpenVPN can be deployed in two ways: you can download and run the official client software yourself, or you can subscribe to a VPN service provider that uses OpenVPN as its underlying technology.
A practical example: if you connect to OpenVPN whilst using public WiFi at a café, your web traffic becomes encrypted. The café's network can see that you are using a VPN, but cannot see which websites you visit or what data you send. Your real IP address (which reveals your approximate location) is replaced by the VPN server's address.
When evaluating VPN services or software, check whether they support OpenVPN alongside other protocols. Some users prefer OpenVPN because it is widely trusted and audited, whilst others favour newer protocols for speed. Performance varies depending on server distance and network congestion. OpenVPN typically uses port 443 or 1194, and some network administrators may block non-standard ports.
If privacy on public networks matters to you, understanding VPN protocols like OpenVPN helps you choose a service that meets your actual security needs rather than just marketing claims.