VPNs Make You Slower - And That Is Unavoidable
Using a VPN slows down your internet. This is an inherent consequence of how VPNs work, not a flaw in any particular service. The key is understanding why the slowdown happens so you can distinguish normal behavior from actual problems.
Three Technical Reasons for Speed Loss
1. Encryption Processing Overhead
VPNs encrypt all your traffic. The process of encrypting data before sending and decrypting upon receipt adds latency. Modern algorithms like AES-256-GCM are designed for speed, but the cost is never zero - especially on mobile devices with limited CPU power.
2. Increased Physical Distance
Without a VPN, data takes the shortest path to its destination. With a VPN, traffic first routes through the VPN server before reaching the target. If you are in Tokyo accessing a US website through a Singapore VPN server, your data travels Tokyo to Singapore to the US instead of directly.
3. VPN Server Congestion
VPN servers handle traffic from many users simultaneously. During peak hours, shared bandwidth and processing capacity become bottlenecks. Services with more servers and better infrastructure experience less congestion.
Speed Characteristics by VPN Protocol
Your choice of VPN protocol significantly impacts speed.
| Protocol | Speed | Characteristics |
|---|---|---|
| WireGuard | Fastest | Lightweight codebase (~4,000 lines), efficient cryptography |
| IKEv2/IPsec | Fast | Excellent for mobile; handles Wi-Fi/cellular switching seamlessly |
| OpenVPN (UDP) | Moderate | Stable and compatible, but 20-30% slower than WireGuard |
| OpenVPN (TCP) | Slow | TCP-over-TCP problem degrades performance; used for firewall bypass |
WireGuard achieves 2-3x throughput and 30-50% latency improvement over OpenVPN in benchmarks. If speed matters, choose a service that supports WireGuard.
Practical Tips to Minimize Speed Loss
- Choose the nearest server: Physically closer servers mean lower latency
- Use WireGuard: Select WireGuard when available
- Avoid peak hours: Servers are most congested during evening hours (8 PM - midnight)
- Use split tunneling: Route only sensitive traffic through the VPN while letting streaming and other traffic go direct. Pair this with a VPN kill switch to ensure sensitive traffic is blocked if the VPN connection drops
- Use wired connections: Eliminate Wi-Fi overhead to isolate VPN-specific speed loss
What Speed Loss Is "Normal"?
- 10-20% loss: Excellent. Achievable with nearby servers and WireGuard
- 20-40% loss: Typical. Common with OpenVPN or mid-distance servers
- 40-60% loss: Acceptable for distant servers or peak hours, but room for improvement
- Over 60% loss: Investigate server congestion, protocol issues, or ISP throttling
To confirm your VPN is working correctly, use IP確認さん to check whether your IP address has changed and run a DNS leak test. If your real IP or DNS servers are still visible, your VPN configuration needs attention.
To learn more about VPN technology, network security books provide comprehensive coverage.