How Does a VPN Work?

When you tap 'Connect' on a VPN app, several things happen quickly. First, your device initiates a cryptographic handshake with the VPN server to verify its identity using digital certificates. This helps prevent man‑in‑the‑middle attacks where a malicious actor pretends to be the VPN server.

Next, both sides agree on encryption keys using a key‑exchange algorithm. These keys are unique to your session and are not transmitted in a way that allows an eavesdropper to trivially recover them.

Finally, the encrypted tunnel is established. Every packet of data you send is encrypted on your device, travels through the tunnel to the VPN server, is decrypted there, and forwarded to its destination on the internet. The response follows the reverse path.

Exact connection times vary by protocol, server distance, and network conditions.

VPN encryption uses symmetric-key cryptography, typically AES-256 (Advanced Encryption Standard with 256-bit keys). AES-256 is the same encryption standard used by the US military and intelligence agencies. To brute-force a 256-bit key, you'd need to try 2^256 combinations — more than the number of atoms in the observable universe.

WireGuard uses a different cipher called ChaCha20-Poly1305, which is equally secure but faster on devices without hardware AES acceleration (like smartphones). The encryption ensures that even if your traffic is intercepted, it appears as random data.

Beyond the cipher itself, VPNs use authentication codes (like HMAC-SHA256 or Poly1305) to verify that data hasn't been tampered with during transit. This protects against both eavesdropping and data manipulation attacks.

For a deeper dive into specific ciphers and their performance characteristics, see our VPN encryption guide.

The tunneling protocol determines how data packets are encapsulated and transmitted.

WireGuard is a modern protocol designed to be fast and efficient, with a relatively small codebase.

OpenVPN is older, widely supported, and can run over TCP or UDP. TCP mode can be helpful on unstable or restrictive networks.

IKEv2/IPSec often works well on mobile because it can handle network switching (Wi‑Fi to cellular) smoothly.

Some providers also ship proprietary protocols. Treat any performance or reported claims as time‑sensitive and verify them using published sources.

Without a VPN, every website you visit sees your real IP address, which reveals your approximate location (city-level accuracy) and ISP. Your ISP logs which IP addresses you connect to, creating a detailed profile of your online activity.

With a VPN, websites see the VPN server's IP address instead. If you connect to a server in Dallas, websites think you're in Dallas. Your ISP sees only a single encrypted connection to the VPN server — no domains, no URLs, no content.

This is why a VPN is essential for privacy, especially since the 2017 repeal of FCC broadband privacy rules that allowed ISPs to sell browsing data. Your IP address is effectively your online fingerprint, and a VPN replaces it with the server's shared IP — making your individual activity much harder to trace.

When you type a website address, your device sends a DNS query to translate the domain name into an IP address. Without a VPN, these DNS queries go to your ISP's DNS servers, giving your ISP a complete list of every website you visit — even if the website itself uses HTTPS.

A properly configured VPN routes DNS queries through the encrypted tunnel to the VPN provider's own DNS servers. This prevents DNS leaks, which occur when DNS queries accidentally go to your ISP despite the VPN being connected.

The best VPNs run their own private DNS servers and include DNS leak protection that blocks any queries from leaking outside the tunnel. When evaluating a VPN, test for DNS leaks using tools like our What Is My IP page or dnsleaktest.com.

A practical VPN security review starts with checks you can repeat on your own device:

• DNS leak protection — run a DNS leak check after connecting
• WebRTC leak protection — confirm your browser is not exposing your real IP
• IPv6 handling — check whether IPv6 traffic is tunneled or blocked
• Kill switch reliability — briefly test disconnect behavior before relying on the app
• Policy clarity — read what the provider says it logs, stores, and shares

Use these checks as buyer due diligence. StatesVPN summarizes public-source information and does not operate a testing lab.