APNG file format is an extension to the Portable Network Graphics (PNG) specification, which allows for animated files that works similar to GIF files, with support for 24-bit images and 8-bit transparency both of which are not available for GIF files.
While APNG competes with the Multiple-image Network Graphics (MNG), which is a more comprehensive format for bitmapped animations built by the same team as PNG. But APNG's advantage is perhaps the smaller library size and the compatibility with older PNG implementations.
Also, it retains backward compatibility with non-animated PNG files, but Twitter is citing a potential cause of seizures in motion-sensitive people for suspending the use of animated PNG image files (APNGs) from its platform.
We recently found a bug that lets you add multiple animated images to a Tweet using Animated PNG files. APNGs ignore our safeguards and can cause performance issues for the app and your device. Today we’re fixing the bug which will no longer allow APNGs to animate when Tweeted.— Twitter Support (@TwitterSupport) December 23, 2019
According to Twitter, there was a bug that allow users to add multiple animated images to a Tweet using Animated PNG files. APNGs ignore the safeguards put in place and can cause performance issues for the Twitter app and your device. So, the fix for the bug which has been pushed out means you will no longer be able to use APNGs with your Tweet.
The company added that existing APNG files uploaded to the platform will not be removed, however the team will look into building a similar feature that’s better for users and their Twitter experience.