Deep packet inspection
Network equipment that examines the structure of traffic rather than only its destination address.
Glossary
SNI
Also called: Server Name Indication
The field in a TLS handshake that names the site being requested, historically sent unencrypted even over HTTPS.
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 tunnel hides SNI from your local network regardless, because the handshake happens at the tunnel exit.
Related terms
DNS leak
When name lookups travel to your ISP’s resolver instead of through the tunnel, exposing every domain you visit.
Terms are defined here because they appear in our scoring rubric or in provider reviews, not to fill a glossary.