OpenVPN UDP vs TCP: which should you use?
OpenVPN can carry VPN traffic over UDP or TCP. The encryption can be the same while the transport behavior is different, so speed, latency and reliability can change even with the same provider and destination.
OpenVPN UDP vs TCP for speed
UDP normally avoids the extra acknowledgement and retransmission behavior of TCP, which can reduce overhead for real-time VPN traffic. TCP may be useful on networks where UDP is blocked or unreliable, but a TCP VPN connection carrying TCP application traffic can also suffer from interacting retransmission and congestion-control layers. The practical result still depends on the route, provider and network.
When OpenVPN TCP can be useful
TCP can be a fallback when a restrictive network does not pass UDP cleanly. It can also behave differently on unstable links because transport recovery happens in TCP itself. That does not make it universally faster or slower, so Secure-VPN keeps UDP and TCP in separate benchmark rows.
Why TCP-over-TCP can hurt some VPN transfers
When an application already uses TCP and the VPN tunnel also runs over TCP, both layers can react to loss and congestion. Their recovery behavior can interact and amplify pauses on a poor route. This is one reason OpenVPN UDP is commonly tested first when the network allows it, while TCP remains valuable as a compatibility option.
Latency and interactive traffic
Video calls, remote desktops and gaming are sensitive to delay as well as throughput. UDP avoids transport-level acknowledgement overhead, but the real latency still depends on the path to the VPN server. Compare the measured latency column rather than assuming the transport alone determines responsiveness.
Compare the measured data
Use Speed by protocol to compare median download, speed retention, latency, destination coverage and confidence from one source location at a time. Provider pages also show separate OpenVPN UDP and TCP rows where enough quality-checked data exists.
OpenVPN vs WireGuard-based protocols
If you are choosing between protocol families rather than only UDP and TCP, read WireGuard vs OpenVPN. For NordVPN specifically, the measured WireGuard-based implementation is NordLynx.