hi Splashm, you might want to try the following (haven't tested this myself): enter about:config into the firefox address bar (confirm the info message in case it shows up) & search for the preference named browser.casting.enabled. double-click it and change its value to true - then there might be a "send video to device" entry in the context menu,when you right-click on html5 videos. since the feature is behind a pref by default, it is in an experimental and probably buggy state still though...

Thanks Phillip, but that does not appear to work. I made the changes recommended, closed Firefox and restarted. Opened Now TV and selected a movie, but there was no way to cast it to Chromecast, and no right click sub menu either. Thanks for the suggestion though.

See also;

• bug 1142521 - disable video/tab casting in Firefox 37 and later

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

Thanks Cor-el, Afraid I could not follow all the bug reports, but summarising it seems that casting causes an issue in Windows firewall with the casting pref. enabled. After I set it to true and restarted Firefox I did not get any form of firewall warning, just no option to cast the video. Is there a context menu that should be active? The only thing that appears with the right click option is the text "Silverlight"? If you click on this option / message, nothing appears to happen other than Firefox then hangs with a message that Firefox is waiting for Silverlight to respond, whichever option you take to this message Firefox has departed this world and ALT+ CTR+ DEL appears to be the only way out of the deadly embrace.

On the basis that I still cannot use Firefox to cast to chromecast, I will ask the question again:

When will Firefox for Windows support Chromecast?