Overall, the most secure protocol is OpenVPN. All the best VPNs support OpenVPN, which is known for its security, speed, and reliability. Many VPNs now also support the WireGuard protocol, which is designed for speed and security and is much more lightweight than OpenVPN — just 4,000 lines of code compared to OpenVPN’s 600,000.
Others include ExpressVPN’s proprietary Lightway protocol and IKEv2 (good for mobile devices). The security of your VPN depends on more than just its protocols, though. You should choose a trusted provider with proven security features. Also, note the provider’s company headquarters and privacy policy to ensure your online activity and personal data are secure.