I love all the upgrades to Firefox PiP over the past year, and one of my favorite additions are the caption support. Some major sites are supported, but other major sites aren't.
I'm not an expert on the underlying framework, but I know Firefox boasted about including compatibility for a few sites that remain incompatible to this day (HBO Max) while other sites I use daily are also incompatible (Invidious, Piped).
If anyone would like to share sites they know work with Firefox PiP Captions, sites which don't, and sites that should, be my guest.
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