Available here: https://www.mozilla.org/en-US/firefox/all/

As far as Plugins for Win64, only Flash and SIlverlight are available in Win64 and it is doubtful if any more Plugins will ever be whitelisted. NPAPI Plugins aren't long for this world and for a few reasons Mozilla is loath to add then to Win64 Firefox.

Hello,

Mozilla's Future Releases Blog says this about Firefox 43: "Firefox 64-bit for Windows, by design, has limited support for plugins and users will notice that certain sites requiring plugins that worked in previous 32-bit versions of Firefox might not work in this 64-bit version."

I hope this anwsers your question.

Gert Van Waelvelde said

Hello, Mozilla's Future Releases Blog says this about Firefox 43: "Firefox 64-bit for Windows, by design, has limited support for plugins and users will notice that certain sites requiring plugins that worked in previous 32-bit versions of Firefox might not work in this 64-bit version."

Thanks to you and the-edmeister for your help.

Here is an article that I think elaborates on what you say: https://blog.mozilla.org/futurereleases/2015/10/08/npapi-plugins-in-firefox/

The answer, as I understand it, would be that Mozilla believes the world would be better off without NPAPI plugins, and would like to hasten that day by not supporting them. This will be true for all versions of FF by the end of 2016. But because the 64 bit Windows FF is late to the party, it will lack functionality throughout the transition period because there will never be NAPAPI plugs developed for it beyond Flash and Silverlight.

So come back a year from now, I take it? Is that fair to say?

Yes, I think that's correct.