To Aelisya and bigon, if you have Extension source viewer you can see (Firefox user 13857193)s code. This isn't spyware and does connects to securely... https://httpspluschecker.virtit.fr

CODE:
if (url.protocol === "http:" || url.protocol === "https:") {
console.log("onGot : " + API)
var host = url.hostname;
xhr.open('GET', API + host, false);
xhr.send();

The addon does what it says and is safe!