Will not work on Windows 10 64bit. Does not recognize that the Add-On is installed, even though it is. As about 350 others have said, this is worthless. Keeps prompting me to download and install a file. Takes you into an endless loop of BS. I stopped trying. How is it possible that they have not fixed this issue. Not like Windows 10 and Firefox are new!

Extension keeps prompting me to download/install in Firefox, even though it's already installed. Unable to activate the Extension despite repeated attempts.

FAIL. Doesn't work on Windows 10 64-bit. I tried to save my Firefox bookmarks to my iCloud account but was unable to. I am repeatedly prompted to download the iCloud Bookmarks extension for Firefox even though it has already been downloaded. Waste of time.

Excellent