Elon Musk tweeted after the disruption that backend upgrades were being completed. 

As the outages spread, the hashtag "#TwitterDown" trended, and by 7:13 pm EST, outage detection website Downdetector reported a surge in users that indicated the social media platform was experiencing outages. More than 9,000 users on Downdetector reported issues. 

Here's a timeline of the outage.