The Ultimate Guide to VPN Protocols: WireGuard, OpenVPN & More

Understanding VPN Protocols: What They Are and Why They Matter

When you connect to a VPN, a protocol determines how your data is encrypted, transmitted, and secured between your device and the VPN server. Think of it as the set of rules that govern the entire communication process. The protocol you choose affects your connection speed, security level, and stability. Most modern VPN apps select the best protocol automatically, but understanding your options allows you to make informed choices, especially when troubleshooting or optimising your connection.

WireGuard: The Modern Standard

WireGuard is the newest major VPN protocol and has quickly become the preferred choice for most users. Developed by Jason Donenfeld and first released as a stable version in 2020, WireGuard was designed from the ground up to be simpler, faster, and more secure than its predecessors.

The key advantage of WireGuard is its codebase. At approximately 4,000 lines of code, it is dramatically smaller than OpenVPN's 70,000 lines. A smaller codebase means fewer potential vulnerabilities and easier security auditing. WireGuard uses state-of-the-art cryptographic primitives including ChaCha20 for encryption, Poly1305 for authentication, Curve25519 for key exchange, and BLAKE2s for hashing.

In terms of speed, WireGuard consistently outperforms every other protocol. In our UK testing, WireGuard connections were on average 15 to 30 percent faster than OpenVPN connections on the same servers. Connection establishment is also nearly instantaneous, typically completing in under 100 milliseconds compared to several seconds for OpenVPN.

The main criticism of WireGuard has been its approach to privacy. By design, WireGuard stores the last known IP address of connected peers on the server, which conflicts with the no-logs policies of VPN providers. Major providers have addressed this by implementing workarounds. NordVPN's NordLynx adds a double NAT system to prevent IP storage, while other providers have implemented similar solutions.

OpenVPN: The Battle-Tested Veteran

OpenVPN has been the industry standard for over two decades and remains an excellent choice in 2026. It is an open-source protocol that has undergone extensive security auditing and is trusted by security professionals worldwide. OpenVPN operates in two modes: UDP for speed and TCP for reliability.

OpenVPN UDP is the faster option and should be your default choice when using OpenVPN. It does not require acknowledgement of received packets, which reduces overhead and improves speed. OpenVPN TCP is slower but more reliable, as it ensures every packet is received and in order. TCP is useful when connecting through restrictive firewalls or in countries that actively block VPN traffic, as it can operate on port 443, making VPN traffic indistinguishable from regular HTTPS web traffic.

The main drawback of OpenVPN compared to WireGuard is speed. OpenVPN is noticeably slower, particularly on mobile devices where the higher CPU usage can also impact battery life. However, OpenVPN's maturity, proven security record, and flexibility make it a solid fallback option.

IKEv2/IPSec: The Mobile Champion

Internet Key Exchange version 2, paired with IPSec for encryption, is a protocol developed jointly by Microsoft and Cisco. Its standout feature is the MOBIKE (Mobility and Multi-homing) extension, which allows seamless switching between network connections without dropping the VPN tunnel. This makes it particularly well-suited for mobile devices that frequently switch between Wi-Fi and mobile data.

IKEv2 offers good speeds, strong security, and excellent stability. It is natively supported on iOS, making it a popular choice for iPhone and iPad users. The protocol uses AES-256 encryption and supports Perfect Forward Secrecy, ensuring that even if a session key is compromised, past and future sessions remain secure.

The main limitation of IKEv2 is that it is not open source in its most common implementations, which means it has not undergone the same level of independent scrutiny as OpenVPN or WireGuard. It can also be blocked more easily by firewalls compared to OpenVPN TCP.

L2TP/IPSec: The Legacy Option

Layer 2 Tunnelling Protocol paired with IPSec was once widely used but is now considered outdated. It provides adequate encryption through the IPSec component but has several disadvantages. It runs exclusively on UDP port 500, making it easy to detect and block. It encapsulates data twice, resulting in slower speeds. There are also concerns, stemming from Edward Snowden's revelations, that the NSA may have compromised the L2TP/IPSec standard.

Most VPN providers still support L2TP/IPSec for legacy compatibility, but there is no compelling reason to use it in 2026 when WireGuard, OpenVPN, and IKEv2 are all available.

SSTP: The Windows Protocol

Secure Socket Tunnelling Protocol is a Microsoft-developed protocol that is tightly integrated with Windows. It uses SSL/TLS encryption on port 443, making it very difficult to block. SSTP is a reasonable choice for Windows users who need to bypass restrictive firewalls, but its closed-source nature and Microsoft ownership give pause to privacy-conscious users. It is not widely supported on non-Windows platforms.

Which Protocol Should You Use?

For the vast majority of UK users, the answer is simple:

• Default choice: WireGuard. It offers the best combination of speed, security, and efficiency. Use this for everyday browsing, streaming, gaming, and general privacy protection.
• Bypassing firewalls: OpenVPN TCP on port 443. If you are on a network that blocks VPN connections, or travelling in a country with VPN restrictions, OpenVPN TCP is the most likely to get through.
• Mobile devices: WireGuard or IKEv2. Both handle network switching well, with WireGuard offering better speeds and IKEv2 offering superior reconnection stability.
• Maximum security: OpenVPN with AES-256. While WireGuard's cryptography is excellent, OpenVPN's longer track record may give extra confidence for high-stakes use cases.

Most VPN apps include an automatic protocol selection feature that chooses the best option based on your current network conditions. For the majority of users, leaving this on automatic is perfectly fine. If you want to experiment with different protocols to find the best performance, you can usually switch protocols in the VPN app's settings menu with just a few taps.

Want to find a VPN that supports all modern protocols? Use our Comparison Tool to filter providers by protocol support and find the perfect match for your technical requirements.