Slack is back after an outage that started around 11.30am NZT.
The US-based company had no immediate word on the cause of the foul-up.
In a blow to many working from home, the workplace messaging service suffered a global outage from late morning.
The failure left many businesses returning to email and phone calls to communicate.
Slack acknowledged the issue on Twitter, writing: "Users have reported general performance issues such as message sending failures and timeouts."
