What exactly is a GIFV?
Imgur introduced “GIFV” in 2014 to cut bandwidth: instead of serving huge animated GIFs, it serves the same animation as an MP4 (or WebM) video that autoplays, loops and has no sound. The .gifv address is actually a small web page wrapping that video, which is why saving it with “Save image as” doesn’t give you a GIF.
Because the content is video, it’s typically 5–10× smaller than an equivalent GIF. Converting back to GIF is useful when you need a real image — for a forum signature, a chat app that only autoplays GIFs, or a slide deck — but expect a bigger file. Keep the width modest and, if needed, run the result through the GIF compressor.
Downloading the video behind a GIFV link
For an Imgur link ending in .gifv, replace the extension with .mp4 and open it: your browser shows the raw video, which you can save with right-click → Save video as. That MP4 converts exactly like any other in MP4 to GIF. If you’d rather keep the small video form, it already is one — there’s nothing to convert; and for turning ordinary GIFs into compact videos, use GIF to MP4.