Glossary · VPN & tunneling

DNS leak

Also calledvpn dns leak

Definition

A DNS leak happens when your device sends DNS lookups outside the VPN tunnel — revealing which sites you are visiting even though the traffic itself is encrypted.

Explanation

In depth

DNS is how your device converts "youtube.com" into an IP address to connect to. If your VPN client is configured to route only HTTP/HTTPS traffic through the tunnel and lets DNS resolve via your ISP, then your ISP sees every domain you look up — a serious leak of what you thought was private. Good VPN clients route DNS through the tunnel by default. Test for DNS leaks with dnsleaktest.com. Web proxies are less prone to this problem because DNS for the destination is resolved by the proxy server, not your device — but your local network still sees a DNS lookup for the proxy domain itself (that is expected and unavoidable).

Related terms

VPNA VPN is a service that routes every network request from your device through an encrypted tunnel to a remote server.DNSDNS is the internet's address book — it translates human-readable domain names like anyproxy.site into IP addresses computers use to connect.WebRTC leakA WebRTC leak exposes your real IP to a website via the browser's WebRTC API — even when a VPN is active — because WebRTC uses STUN outside the tunnel.IPv6 leakAn IPv6 leak happens when your VPN tunnels IPv4 traffic but lets IPv6 traffic bypass the tunnel — exposing your IPv6 address to destinations.

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