Facebook-owned WhatsApp went offline on New Year's Eve, leaving thousands of Android and iOS users in America, Europe and Canada unable to access the app.
The outage that started at 4:30 p.m. UK time left users with issues, including not being able to send replies to existing chats, start new conversations and access the app's Web service.
People who were affected by the Web service disruption were greeted with an error message that said "WhatsApp Web requires a working Internet connection, which you don't have at the moment."
DownDetector, a site which gives an overview of mobile and Internet services in real time, revealed that the outage was experienced in the United States and Europe.
In a few instances, some users reported that they could receive messages, but they were not able to respond.
A spokesperson for WhatsApp confirmed the interruption of the service to MailOnline.
"Some people have had trouble accessing WhatsApp for a short period today," said the spokesperson. "We're working to restore service back to 100 percent for everyone and we apologize for the inconvenience."
It was reported that the service was initially restored only to crash again a few minutes later.
The reason behind the outage is unknown, but people speculated that the problem could have been caused by a huge spike in traffic on New Year's Eve, which is usually the app's busiest day.
In September, WhatsApp CEO Jan Koum revealed that the app has 900 million active users every month.
Launched in 2009, WhatsApp has developed into a global messaging platform. The app makes it possible for users to send text and voice messages without getting charged by carriers.
WhatsApp gained more traction when it was bought by Facebook for $19 billion in 2014. The deal became one of Silicon Valley's biggest, making the app's cofounders Jan Koum and Brian Acton billionaires.
At the moment, WhatsApp is the most widely used instant messaging client in the world.
In the meantime, users took to Twitter to complain about the issues they encountered when trying to access the messaging service. Some are actually humorous.
Let us take a look at a few of these tweets.
#Whatsapp is down! Time to go back to SMS messages? We could even have a proper conversation with those around us!
— IG:@basemaguilera (@basemaguilera) December 31, 2015
Whatsapp being down actually saved us from all those "...Forward this message to 10 people or remain in 2015..." texts — King A (@AdamMaina_) January 1, 2016
Imagine if WhatsApp, Twitter, Facebook, Instagram all went down at the same time, we might have to actually get a life - Ahmad Mirza (@MirxaAhmad) April 26, 2014