KotoVPN

Glossary

SNI

Also called: Server Name Indication

What is SNI?

SNI is the field in a TLS handshake that names the site being requested, historically sent unencrypted even over HTTPS. It is how a network can see which site you are visiting despite the connection being encrypted, and it is the basis of several national filtering systems.

Why it matters

It is how a network can see which site you are visiting despite the connection being encrypted, and it is the basis of several national filtering systems.

What most explanations leave out

Encrypted Client Hello addresses this, but deployment depends on both the browser and the site. A VPN hides SNI from your local network because the handshake is encapsulated inside the tunnel — not because the handshake moves. TLS is still negotiated end to end with the origin server, so the VPN operator and the exit server’s upstream network can read it exactly as your ISP would have.

Related terms

Deep packet inspection

Network equipment that examines the structure of traffic rather than only its destination address.

DNS leak

When name lookups travel to your ISP’s resolver instead of through the tunnel, exposing every domain you visit.

Questions

What is SNI?
The field in a TLS handshake that names the site being requested, historically sent unencrypted even over HTTPS.
Why does SNI matter when choosing a VPN?
It is how a network can see which site you are visiting despite the connection being encrypted, and it is the basis of several national filtering systems.
What do most explanations of SNI leave out?
Encrypted Client Hello addresses this, but deployment depends on both the browser and the site. A VPN hides SNI from your local network because the handshake is encapsulated inside the tunnel — not because the handshake moves. TLS is still negotiated end to end with the origin server, so the VPN operator and the exit server’s upstream network can read it exactly as your ISP would have.

Terms are defined here because they appear in our scoring rubric or in provider reviews, not to fill a glossary.