When request is made over HTTPS, the server name in the URL may not be encrypted, only the path to the resource will be encrypted.<p>i.e.<p>if you type <a href="https://www.example.com/path/to/my/resource?show=pretty" rel="nofollow">https://www.example.com/path/to/my/resource?show=pretty</a>
then the www.example.com may be sent in plain text
only the path part will be encrypted.
TL;DR: SNI sends <i>hostname</i> (not whole URL) in plaintext, ESNI (encrypted) is not widely supported (not in Chrome, off by default in Firefox, visited domain also needs to support it).