Finally an Add-On that works Noté 5 sur 5 étoiles
Contrary to Force-TLS which doesn't work at all since Fx 36 (you can add domains to the list, but that's all you can do, they will still open at HTTP), this add-on really works and does what it is supposed to do.
UPDATE (October 9, 2015):
Now that the UI has been improved (see comment below) my only real point of criticism has vanished, so this add-on now deserves 5 stars.
The user interface has been improved in version 1.0.4.
Lightweight and 100% functional Noté 5 sur 5 étoiles
In order to test https availability (and reverse to http if not) a simple bookmarklet found on the Web :
Switches http to https and backwards, et voila
Perfect companion for 'Enforce Encryption'
Lightweight security tool Noté 5 sur 5 étoiles
This addon is a sweet idea: sites such as Google Search, Wikipedia, and YouTube offer encryption but don't usually ask the user for their preferences. Rather than adding https:// to the beginning of a URL for every session for a site, you can check the box and have your browser remember.
Found no bugs with this addon, it works great.
A technical rundown of what Strict-transport security is can be found at https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security