Twitter started supporting animated GIFs. But there’s a catch! What Twitter ends up showing you isn’t actually a GIF at all. EVERYBODY PAAANIIIIIIC.
Note: don’t actually panic. This isn’t a bad thing. Quite the contrary.
As noticed by the folks over at Embedly, the “GIFs” that end up in your Twitter feed aren’t actually GIFs at all. They’re technically not even really image files in a strict sense — they’re more like video files without sound. They’re MP4s, embedded with the HTML5 video tag. Even if you upload a GIF, it’s converted into an MP4.
And why is this good? Embedly explains:
GIFs are terrible at compression… A GIF is literally a sequence of independent images squeezed into the same file. An mp4 video can take advantage of all kinds of fancy compression techniques like keyframes and forward-predictive frames.
If most of your users are on mobile, this is a huge win. Even desktop users will notice better performance on a page with many GIFs.
(Via this Adam Gurri tweet.)