😀 HTTP/1.1 Upgrade header
The Upgrade header field is a HTTP header field introduced in HTTP/1.1. In the exchange, the client begins by making a cleartext request, which is later upgraded to a newer http protocol version or switched to a different protocol.
- WebSocket uses this mechanism to set up a connection with a HTTP server in a compatible way.
- HTTP/2 uses this to setup a compatible HTTP connection.
16 Sep 2017