Meta Platforms Inc (NASDAQ:FB) shares dipped in pre-market trading after WhatsApp went down for around two hours this morning.
Users around the world had trouble sending and receiving messages, though the service is said to be back and up running again now.
Over 12,000 reports were posted within half an hour, Down Detector said, from the UK, Australia, Ukraine, India, Hong Kong, Singapore and South Africa.
Meta confirmed the problem was fixed but gave no reason for the outage, which occurred between 8:00 am and 10:00 am.
Facebook owner Meta said: "We know people had trouble sending messages on WhatsApp today.
"We have fixed the issue and apologise for any inconvenience."
The app, which has been used by government ministers in recent times and offers end-to-end encryption for messages, is often used for group chats, audio and video calls and social/work activities.