works great with duck duck go's extension. These are the only 2 you need.

Please add a button (function) allow only HTTPS and block all http. Thank you.

Works well in most cases but does not revert to http on a mixed page causing incorrect display.

After installing you will never be able to search a word from url bar.
Just do not install it!

Very good Addon.
I was using HTTPS Everywhere before which is crap (did not redirect to HTTPS on all websites).

Work in firefox 58.0.2
_______________
Всё работает на Firefox 58.0.2

It does nothing on firefox 57.

It doesn't revert to http when encounters error. It also blocks some scripts in http only pages.

Seems to do the same thing the other guys do. I have not experienced any issues.

.