Slack Technologies said it expects fiscal 2020 revenue to grow as much as 50% but the owner of the workplace instant messaging app anticipates a loss for the year, ahead of its listing this month. 

Slack is one of the most high-profile companies left to list their shares in 2019, following initial public offerings of Pinterest, Zoom Video Communications and Beyond Meat. 

However, the struggles of ride-hailing company Uber Technologies and its smaller rival Lyft, the two biggest IPOs so far this year, have cast a pall over new tech listings. 

San Francisco-based Slack, whose customers include Electronic Arts, Nordstrom and Ford, said it was seeing strong user retention and engagement rates.

This comes ahead of its plans to go public via a direct listing instead of an IPO on June 20. 

Slack said it continued to see 'broad adaption' across a variety of industries and geographies in the first quarter, with user retention and engagement rates rising. 

"Users, (who) are paid customers spend more than nine hours a day connected to Slack, and 90 minutes actively using the platform on a typical workday," chief executive Stewart Butterfield said on a conference call. 

The company, which competes with platforms such as Microsoft Teams - a free chat add-on for Microsoft's Office365 users - forecast fiscal 2020 revenue in the range of $590-600m, representing growth of 47% to 50% over the previous year. 

Slack expects an adjusted operating loss between $192m and $182m and forecast full-year billings of $725m to $745m, up 40% to 44% from a year earlier. 

Slack ended the first quarter with 95,000 paid customers and posted 67% growth in quarterly revenue at $134.8m. 

The company reported an adjusted operating loss of $33.8m for the quarter, compared with a $20.2m loss a year earlier. 

The company said it expects second-quarter revenue to grow by 51% to 53% to a range of $139-$141m, with an adjusted loss of between $77-75m.