My current hassles with Firefox, Flash, and (HTML5) video
When I've written before about my extensions, I've said that I didn't bother with any sort of Flash blocking because NoScript handled that for me. The reality turns out to be that I was sort of living a charmed life, one that has recently stopped working the way I want it and forced me into a series of attempts at workarounds.
For a long time, things worked this way with just NoScript. Then at some point recently this broke down; if I relied only on NoScript, YouTube videos either would never play or would autoplay the moment the page loaded. If I turned on Firefox's 'ask to activate' for Flash, Firefox enabled and disabled things on a site-wide basis (so the second YouTube video I'd visit would autoplay). I wound up having to add two extensions to stop this:
is the classic Flash blocker. Unlike Firefox's native 'ask to
activate', it acts by default on a per-item basis, so activating
one YouTube video I watch doesn't auto-play all future ones I
look at. To make Flashblock work well I have disabled NoScript's
blocking of Flash content so that I rely entirely on Flashblock;
this has had the useful side effect of allowing me to turn on
Flash elements on various things besides YouTube.
stops YouTube autoplaying HTML5 videos. With both Flashblock and
StopTube active, YouTube winds up using Flash (which is blocked
and enabled by StopTube). I don't consider this ideal as I'd rather
use HTML5, but YouTube is what it is.
As the name of this addon sort of suggests, StopTube has the
drawback that it only stops HTML5 video on YouTube itself. HTML5
video elsewhere are not blocked by it, including YouTube videos
embedded on other people's pages. So far those embedded videos
aren't autoplaying for me, but they may in the future. That might
(An energetic person might be able to make such an addon starting from StopTube's source code.)
Some experimentation suggests that I might get back to what I want with just NoScript if I turn on NoScript's 'Apply these restrictions to whitelisted sites too' option for embedded content it blocks. But for now I like Flashblock's interface better (and I haven't been forced into this by being unable to block autoplaying HTML5 video).
There are still unfortunate aspects to this setup. One of them is that Firefox doesn't appear to have an 'ask to activate' (or more accurately 'ask to play') option for its HTML5 video support; this forces me to keep NoScript blocking that content instead of being able to use a nicer interface for enabling it if I want to. It honestly surprises me that Firefox doesn't already do this; it's an obviously feature and is only going to be more and more asked for as more people start using auto-playing HTML5 video for ads.
(See also this superuser.com question and its answers.)