Millions of people rely on Facebook to get online. The outage left them stranded.

One of the last messages that Vaiva Bezhan sent on Facebook Messenger on October 4 was incredibly time-sensitive. The Lithuanian photojournalist is co-organizer of the Afghan Support Group, one of many volunteer initiatives trying to help evacuate vulnerable Afghans in the wake of the Taliban takeover. She was writing to ask if she could add someone to a flight manifest for one of the few volunteer-coordinated evacuation flights still leaving the country, but then all Facebook’s services—including Facebook.com, WhatsApp, Messenger, and Instagram—suddenly became unavailable. The outage was due to changes to Facebook’s backbone routers, according to the company. In total, Facebook’s apps and sites were down for almost six hours. For much of the world, Facebook has become “synonymous with the internet,” says Sarah Aoun, vice president for security at the Open Technology Fund, a US nonprofit that supports technology projects like the private browser Tor and encrypted message service Signal. That made the outage the equivalent of nothing less than “a big infrastructure collapse,” she says. For many internet users in the United States, the outage was a minor annoyance. But for the millions of people around the world who rely on Facebook’s products to access the internet, including Afghans that already feel abandoned by the international community's withdrawal in mid-August, the sudden downtime was far more serious.