A survey of users, admittedly conducted by the firm itself, suggests that team productivity increases by around a third when they start using the software, primarily by reducing internal e-mail and meetings. Slack has decided to open itself up to other apps, becoming a platform by which employees can log into and use other software tools. Today it has 2.7m daily active users, up from 1m last June. Around 800,000 of them are paying subscribers; their firms pay around $80 or more a year for each employee using the service. The firm has $75m in annual recurring revenue and is breaking even, says Mr Butterfield.
Slack's rise points to three important changes in the workplace. First, people are completing work across different devices from wherever they are, so they need software that can work seamlessly on mobile devices. Messaging naturally lends itself to this format. Second, communication is becoming more open. Just as offices went from closed, hived-off rooms to open-plan, Slack is the virtual equivalent, fostering a collaborative work environment, says Venkatesh Rao of Ribbonfarm, a consultancy. Slack's default setting is to make conversations public within a firm.
Third, software firms are trying to automate functions that used to be done by people in order to make employees more productive. Slack has made a big push into “bots”, algorithms that can automate menial tasks which used to be done by humans. Slack offers bots that compile lunch orders and projects' progress reports, or generate analytics on demand. In the future employees will be able to chat with software agents to get more done, working alongside bots as well as their peers.
Mr Butterfield is not the typical leader of a striving startup. Called “Dharma” by his hippie parents, he spent his early years on a commune with no running water or electricity; he changed his name to Daniel Stewart when he was 12.