Google has announced plans to discontinue support for Silverlight in the Chrome browser in September.

As far as I know, there are no changes planned for Firefox's support of Silverlight and other NPAPI plugins.

For Win64 Firefox builds as of 41.0 only the 64-bit Flash Player is white listed to run in Win64. The Firefox 41.0 Release may be the first to have Win64.

You can still use 32-bit Firefox and all 32-bit NPAPI plugins installed on Windows system then. The 64-bit Mac OSX and Linux Firefox will still be able to use any NPAPI 64-bit Plugins.

There is no real Silverlight support for Win64 Firefox builds anyways.

Amazon.com only offers the Silverlight plug in for watching video content on the Firefox browser. I used to be able to use the Flash player, but that has been discontinued. When I try to download Silverlight I am told by the install program that my operating system does not support the 64bit version of silverlight, even though I am running Vista64 Ultimate. They have tried to help me but have no answers that I have not already tried. What is the HTML5 player, and will Firefox support it in the future?

See also:

• bug 1187005 - Some plugins (Microsoft Silverlight, Java,...) are not recognized as installed with Firefox 64-bit build on Win64

Please do not comment in bug reports
https://bugzilla.mozilla.org/page.cgi?id=etiquette.html

Hi Kapryan, as noted in your other thread, Firefox for Windows uses the 32-bit version of Silverlight because Firefox for Windows is a 32-bit application. https://support.mozilla.org/questions/1086485

Kapryan said

What is the HTML5 player, and will Firefox support it in the future?

Firefox for Windows already supports HTML5 video playback on YouTube and other sites (except: MP4 doesn't play on Windows XP). It's up to the site to specify whether it wants to use that capability or use a plugin. I don't know what Amazon is thinking.

Kapryan said

Amazon.com only offers the Silverlight plug in for watching video content on the Firefox browser. I used to be able to use the Flash player, but that has been discontinued. When I try to download Silverlight I am told by the install program that my operating system does not support the 64bit version of silverlight, even though I am running Vista64 Ultimate. They have tried to help me but have no answers that I have not already tried. What is the HTML5 player, and will Firefox support it in the future?

Are you using 32-bit Firefox or trying to use Win64 Firefox? which cannot run on 64-bit Vista. If 32-bit Firefox you need 32-bit Plugins even though you have 64-bit Vista.

The Win64 Firefox builds from mozilla.org requires Windows 7, 8 or 10 as the Win64 Firefox builds cannot run on 64-bit WinXP, Vista or servers.