At the moment, officially, you can only cast to Chromecast from the mobile browser, the desktop browser does not support it.

At the moment, officially, you can only cast to Chromecast from the mobile browser, the desktop browser does not support it.

I can't find it in Firefox for Android. Where can I find this?

You can find it on Mozillas site, in the Playstore , or on F-droid (Open-Source App-store)

If firefox desktop can include the Google Widevine plugin for playing DRM content, why not a chromecast plugin? Assuming google has no reason to block it (and plenty to support it), what is Mozilla's position on chromecast for firefox on desktop?

If firefox desktop can include the Google Widevine plugin for playing DRM content, why not a chromecast plugin? Assuming google has no reason to block it (and plenty to support it), what is Mozilla's position on chromecast for firefox on desktop?

The integration of Widevine was associated with a heavy discussion at Mozilla. The aim of Mozilla is to create a completely free and OpenSource Webbrowser, but both, Widevine and Google Cast are propretary technologies. The difference is, that the W3C definied EME (Encrypted Media Extensions) as a web-standard. This decision was also very controversial and because of this the ElectronicFontierFoundation even left the W3C. Finally the Firefox developers decided to implement the webstandard and thereby Widewine (because of its high spread), because its required for the big platforms as Netflix, Amazon, etc., and a cutout would impact their marked-share very strongly. Coromecast therefore is not absolutely required and more like a comfort-feature.