Why a VPN slows your connection, and what to do
Every VPN slows a connection down — the traffic no longer goes directly but through an intermediate server. The question is by how much: the gap between a careful setup and a careless one runs into multiples.
Distance to the server
The dominant factor is physical distance. Traffic to the Netherlands and back covers a few thousand extra kilometres, and that adds latency no amount of optimisation removes. From Moscow to a European server the ping usually sits at 40-60 ms against 5-15 ms direct. Page loads barely notice; games and video calls do. The rule is simple: pick the nearest country unless a specific location is what you need for a particular service.
The protocol and its overhead
Every protocol adds its own share of bookkeeping. Older designs like OpenVPN over TCP give up as much as 20% of throughput: encryption, encapsulation, and TCP over TCP — the well-known problem where two retransmission mechanisms fight each other. Hysteria2 runs over UDP and avoids that entirely, with overhead closer to 5%. That, rather than its being newer, is why we made it the default.
Packet loss, the hidden cause
If speed drops in bursts rather than evenly, packet loss is almost certainly the cause. Over TCP each loss stalls the stream until retransmission, and at 2-3% loss speed falls by multiples rather than percentages. Ping will tell you: if some packets never come back, you have found it. Hysteria2 holds up considerably better in those conditions, because it recovers losses without stalling the other streams.
Throttling by the provider
Some providers deliberately slow encrypted traffic, or traffic on unusual ports. It is not blocking but throttling, and it is hard to spot: the connection works, only slowly. The tell is that VPN speed is consistently low at any hour and on any server while direct speed is fine. Switching protocol usually gets around it: if UDP is being throttled try the TCP entry, and the other way round.
What to check, in order
Measure your speed without the VPN first — without a baseline there is nothing to compare against. Then switch to the nearest country, which is often enough on its own. Next try the other protocol for the same country: a large difference means your network treats UDP and TCP differently. And check the time of day — evening congestion on the backbone produces a dip that has nothing to do with the VPN.