Ah good thing, so imgur abstracts extensions apparently

Better if you request with .gifv extension, then it's a much smaller (than a gif) html5 video)

The only issue with gifv is that if you open one on iOS it will pause whatever music you're listening to at the time. Kind of a bummer and something that will hopefully eventually get fixed.

I think that makes sense as I believe in their system the identifier will be

W1X1qFI which happens to be the url/filename and is auto-generated it ignores the extension

instead of throwing a 404.

For a second there I though they'd done something really clever with progressive jpegs!