Slack — nearing its fourth anniversary since launching to the public — is not a passing fad. The communications service for companies and groups is now a tool that six million people use every day, up from about four million a year prior — despite increased competition from much larger rivals like Microsoft and Facebook.

This year, Slack — represented on the Recode 100 by CEO Stewart Butterfield and VP of Product April Underwood — launched a new version of its service tailored for big corporate customers. And it debuted a new — potentially very useful! — feature that lets teams in different companies chat within a shared Slack channel. (It also raised another $250 million and passed $200 million in annual recurring revenue this past summer.)

One big question is whether Slack will mature into an interface for more of your work life — or if will remain mostly a chat room. For now, it seems Slack is still mostly counting on other companies to integrate those features. Slack says 90 percent of its paid teams actively use add-on apps. And the company has an $80 million fund to invest in companies building promising apps for its ecosystem.

This article originally appeared on Recode.net.