HTTPS
Hypertext Transfer Protocol Secure (HTTPS) is an extension of the Hypertext Transfer Protocol (HTTP). The protocol is therefore also referred to as HTTP over TLS, or HTTP over SSL.
HTTP vs HTTPS
an unencrypted HTTP request reveals not just the body of the request, but the full URL, query string, and various HTTP headers about the client and request:
An encrypted HTTPS request protects most things[1]:
What information does HTTPS not protect?
While HTTPS encrypts the entire HTTP request and response, the DNS resolution and connection setup can reveal other information, such as the full domain or subdomain and the originating IP address, as shown above.
Additionally, attackers can still analyze encrypted HTTPS traffic for “side channel” information. This can include the time spent on site, or the relative size of user input.
HTTPs and HTTP/2
While HTTP/2 does not require the use of encryption in its formal spec, every major browser that has implemented HTTP/2 has only implemented support for encrypted connections, and no major browser is working on support for HTTP/2 over unencrypted connections.
This means that in practice, the major performance benefits of HTTP/2 first require the use of HTTPS.