Twitter recently added Animated PNG support to their mobile app, but today the company decided to roll back support due to the risk they could be used to attack photosensitive epileptics.
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
The issue is that APNGs ignore auto-play settings, meaning epileptics can be surprised by flashing images tuned to provoke seizures. While Twitter said no-one has so far been injured, the risk if not theoretical, as trolls have in the past and recently attacked epileptics by taking over hashtags used by the community.
Twitter users can still use gifs, which can be prevented from animating using auto-play settings.