The most common causes
Encryption and encapsulation add a small amount of data and processing. The route through the VPN server may be longer than the direct route, increasing latency. The server, the provider’s network, local Wi-Fi or the access connection may also be congested.
Maximum throughput often depends on the slowest part of the chain. A single test therefore cannot attribute the problem to the protocol or server.
- Distance and routing quality to the server.
- Congestion on the Wi-Fi network, internet connection or server.
- Device performance and protocol overhead.
- Packet loss, unsuitable MTU or a filtered network.
- The method and server selected by the test tool.
A useful testing method
Use the same device, the same physical location and, if possible, a wired connection. Stop background downloads. Measure several times without the VPN, then with a nearby server, at the same times of day.
Record download speed, upload speed, latency and, especially, packet loss. The median of several measurements is more useful than the single best result.
What to check, in order
Local network
Compare Wi-Fi with a wired connection, then restart the access point if necessary.
Nearby server
Choose a location that is closer geographically and in network terms.
Protocol
Compare WireGuard and OpenVPN when the platform allows it.
Application
Update the device and close resource-intensive tasks.
Context
Test at another time or on another network to isolate congestion.
Sources and references
Interpret results without overpromising
Higher latency is normal when the route becomes longer. Throughput may sometimes be higher with a VPN if routing changes favourably, but this is not guaranteed.
If the issue occurs on only one site, that site or an intermediary may be limiting traffic. If the entire connection drops, check the kill switch before concluding that the internet connection has failed.
Useful information for support
Provide the platform, protocol, selected location, approximate time, network type and comparable results with and without the VPN. Never send your password or a private key.
FuzeVPN does not promise a minimum speed or permanent availability of any location. Troubleshooting must remain tied to the observed case.