The Observatory measures site's compliance with the Web Security guidelines [1] and the Server Side TLS guidelines [2]. It's primarily meant as a helper for website developers and operators.
You need https to guarantee data in transit is not being modified between your server and web clients. ISPs, for instance, have a bad tendency to inject tracking cookies in http traffic.
Example run on addons.mozilla.org: https://observatory.mozilla.org/analyze.html?host=addons.moz...
The Observatory measures site's compliance with the Web Security guidelines [1] and the Server Side TLS guidelines [2]. It's primarily meant as a helper for website developers and operators.
[1] https://wiki.mozilla.org/Security/Guidelines/Web_Security
[2] https://wiki.mozilla.org/Security/Server_Side_TLS
(disclaimer: I work on security at Mozilla)