WhatsApp users around the world were left without the messaging service for 45 minutes earlier.
People just had a spinning buffer wheel when trying to connect.
No reason's been given but it's understood Facebook - which owns the app - is investigating.
It's used by more than 1-billion people globally.
The #whatsappdown is trending across social media.
Here's a flavour of what's up while WhatsApp is down;
Everyone is checking Twitter to see if whatsapp is down 😂🤣😆#WhatsappDown 👨🏽💻 pic.twitter.com/lsnMBUP2wL
— Sharon (@ShazzySethy) November 3, 2017
When it's back up and you've zero notifications #WhatsappDown pic.twitter.com/DYmv1KmsYa
— mother.of.foodies (@rachel___ayg) November 3, 2017
WhatsApp Users Right Now 😕#whatsappdown pic.twitter.com/mKRMc5fDsC
— Hassan Roonjho® (@Hassan_Roonjho) November 3, 2017