HTTP Status Codes 1xx

100 Continue - This tells the clients that it should continue with its request. This informs the client that the initial part of the request has been received and accepted by the server. Now client should continue by sending the remaining part. If the request has been completed then ignore this response. The server will send a final response after all requests completed.

101 Switching Protocols - Tells the client that server is going to switch to a new protocol for the current connection. The new protocol will be mentioned in the Upgrade message header field. Server will do this only if there is a better way to communicate with the new protocol. For example server may switch to a new version of http protocol instead of old one whenever requied. i.e. instead of HTTP/1.0 server may swich to HTTP/1.1