Constant actix_web::http::header::SEC_WEBSOCKET_EXTENSIONS

pub const SEC_WEBSOCKET_EXTENSIONS: HeaderName;

The |Sec-WebSocket-Extensions| header field is used in the WebSocket opening handshake. It is initially sent from the client to the server, and then subsequently sent from the server to the client, to agree on a set of protocol-level extensions to use for the duration of the connection.