How Does a VPN Work? (Simple Explanation)

How a VPN Works

A VPN works by creating an encrypted connection (tunnel) between your device and a remote server operated by the VPN provider. All your internet traffic passes through this tunnel, making it unreadable to anyone who might intercept it - your ISP, network administrators, or hackers on public Wi-Fi.

The process involves three key technologies: encryption (scrambling your data), tunneling (wrapping encrypted data in a transport layer), and authentication (verifying both your device and the server are legitimate).

Encryption Explained

When you send data through a VPN, it's encrypted using AES-256-GCM - the same standard used by intelligence agencies and financial institutions. Here's what happens:

1. Your VPN app generates an encryption key unique to your session
2. Every packet of data leaving your device is encrypted with this key
3. The encrypted data is unreadable - it looks like random noise to anyone intercepting it
4. Only the VPN server (which has the matching key) can decrypt it

AES-256 has 2^256 possible key combinations - more than the number of atoms in the observable universe. Brute-forcing this encryption with current technology would take billions of years. It is considered unbreakable.

VPN Tunneling

Tunneling means encapsulating your encrypted data inside a standard internet packet. Think of it like putting a sealed letter (your encrypted data) inside a regular envelope (the outer packet) that can travel through the postal system (the internet).

The outer packet is addressed to the VPN server. Network equipment along the way (your router, ISP, internet backbone) can see the outer addressing but cannot access the sealed letter inside. When it reaches the VPN server, the outer envelope is removed and the inner data is decrypted and forwarded to its destination.

VPN Protocols

A VPN protocol defines how the tunnel is created and maintained. Different protocols offer different balances of speed, security, and compatibility:

• WireGuard: Newest protocol. Fastest speeds, minimal code (4,000 lines vs 400,000+ for OpenVPN), excellent security. Used by most modern VPNs. Our recommended default.
• OpenVPN: Established since 2001. Highly configurable, works everywhere, slightly slower. Good fallback when WireGuard is blocked.
• IKEv2/IPSec: Fast on mobile devices, handles network switches well (Wi-Fi to cellular). Built into most operating systems.
• NordLynx: NordVPN's WireGuard implementation with added privacy (double NAT). Fastest in our ratings.
• Lightway: ExpressVPN's proprietary protocol. Open-source, fast, uses wolfSSL. Connects in under 1 second.

DNS and Leak Protection

DNS (Domain Name System) translates website names (google.com) into IP addresses. Without protection, DNS requests can leak outside the VPN tunnel, exposing which sites you visit.

Quality VPNs run their own private DNS servers and force all DNS queries through the encrypted tunnel. They also include:

• DNS leak protection: Ensures all DNS queries use the VPN's servers, not your ISP's
• IPv6 leak protection: Blocks IPv6 traffic that might bypass the IPv4 VPN tunnel
• WebRTC leak protection: Prevents browser WebRTC from revealing your real IP
• Kill switch: Cuts all internet if the VPN drops, preventing unencrypted data from leaking

Why VPNs Affect Speed

VPNs reduce speed for two reasons:

1. Encryption overhead: Processing data through AES-256 adds computation time. Modern CPUs handle this efficiently - top VPNs lose only 10-15% of speed.
2. Routing distance: Your data travels to the VPN server before reaching its destination. A nearby server adds minimal distance; a distant server adds more latency.

In our ratings against a 487 Mbps reference baseline, the best VPNs retain 83-89% of speed. The slowest retained 78%. For most users on 50-200 Mbps connections, the speed reduction is imperceptible in daily use.

To minimize speed loss: use WireGuard (fastest protocol), connect to the nearest server, and choose a provider with a large server network to avoid congestion.