Twitter bans animated PNG files after online attackers targeted users with epilepsy

Twitter is banning animated PNG image files (APNGs) from its platform, after an attack on the Epilepsy Foundation’s Twitter account sent out similar animated images that could potentially cause seizures in photosensitive people.

Twitter discovered a bug that allowed users to bypass its autoplay settings, and allow several animated images in a single tweet using the APNG file format.

“We want everyone to have a safe experience on Twitter,” the company says in a tweet from the Twitter Accessibility handle. “APNGs were fun, but they don’t respect autoplay settings, so we’re removing the ability to add them to Tweets. This is for the safety of people with sensitivity to motion and flashing imagery, including those with epilepsy.”

Tweets with existing APNG images won’t be deleted from the platform, but only GIFs will be able to animate images moving forward. According to Yahoo, Twitter has further clarified that APNG files were not used to target the Epilepsy Foundation, but the bug meant such files could have been used to do so in the future had Twitter not moved to squash it.

The attacks on the Epilepsy Foundation’s Twitter handle occurred last month — National Epilepsy Awareness Month — with trolls using its hashtags and Twitter handle to post animated images with strobing light effects. It’s not clear how many people may have been affected by the attack, but the foundation said it’s cooperating with law enforcement officials and has filed criminal complaints against accounts believed to have been involved.

An animated image can be considered a deadly weapon, a Texas jury found in 2016, after a man sent a flashing GIF to journalist Kurt Eichenwald, who has epilepsy. The image did indeed cause Eichenwald to have a seizure.

Twitter said Monday it will “look into building a similar feature that’s better for you and your Twitter experience” in lieu of APNGs.