[sparky_z]

They don't work reliably (some things still autoplay), and sometimes they break the media entirely or don't discriminate between things you actually want to autoplay. For example, the one I currently have installed also blocks "gifv" files from autoplaying in the browser, even though there's no play button to click on. Every time I click on a reddit link that turns out to be a gifv file on imgur, it stays frozen on the first frame and I have to click on "view image", manually change the url to "gif", and reload it. As others here have mentioned, they also tend to break youtube in odd ways. It feels like there are a million little annoyances like that. Back in the "flash era", click-to-play was effortless.

[RHSeeger]

When you right click on the gifv, there should be an option to "Show Controls", which allows you to start/pause/etc it.

[sparky_z]

Holy crap, that's really helpful. Thank you!

But from the user perspective... how was I ever supposed to guess that?

[Arnavion]

FYI the exact wording depends on the browser, but all HTML5 video elements will have that context menu option. And other options like "Copy URL", "Loop", etc. depending on the browser.

Of course some websites like youtube override the context menu event to prevent that from showing.

[Zirro]

While it is hardly a discoverable feature, you can override custom context menus (at least in Firefox) by holding SHIFT and clicking.

[voltagex_]

Many thanks. I wonder how many other features I'm missing out on..

[cyborgx7]

There is actually no such thing as a gifv "file format". gifv is just a html page with an embedded webm or mp4 file that hides the standard controls and loops automatically.

[0_00_0]

Yeah that does sound annoying. Have you tried contacting the extension maker? Perhaps they can add that to the list of fixes/features on their next update?