Countless iOS apps experienced problems launching Wednesday evening, according to multiple reports on Twitter and crowdsourced user reports on Downdetector. The issues seem to have started around 6:30PM ET, and Spotify, TikTok, Pinterest, Tinder, and more were affected, according to Downdetector. I personally experienced problems with Spotify and GrubHub, but they are both working for me now, so it seems apps are starting to starting work as normal again.

The issue was caused by an apparent problem with a Facebook software development kit (SDK) tool that’s used to power sign-in features for many of the apps. Many developers reported problems with the SDK in this thread on GitHub. You didn’t need to be logged into the apps via Facebook to be affected by the crashes — I wasn’t able to open a fresh install of Spotify from the App Store, for example.

“Earlier today, a new release of Facebook included a change that triggered crashes for some users in some apps using the Facebook iOS SDK,” a Facebook spokesperson said in a statement to The Verge. “We identified the issue quickly and resolved it. We apologize for any inconvenience.”

A source with knowledge of the situation told The Verge that Facebook had disabled a server configuration update that triggered its SDK to cause apps using it to crash. In the GitHub thread, a user who appears to be a Facebook engineer said the company had reverted the server side change causing the issue and that the change may take time to propagate.

The below tweets from developer Guilherme Rambo summarize the situation, and Rambo also offers a suggestion about what Apple could do to prevent something similar from happening in the future.

Apple has not replied to a request for comment.

Update, May 6th, 11:42PM ET: Added statement from Facebook.

https://www.theverge.com/2020/5/6/21250023/facebook-sdk-login-spotify-tinder-tiktok-ios-iphone-crash