Slack today introduced shared channels, a way for companies to create ongoing joint chatrooms to do business together. The feature, which will be available to paid users of Slack, can now be accessed through an open beta program. If it succeeds, it could build a powerful network of companies that rival communication apps will struggle to displace.

The idea behind shared channels is to let companies that interact frequently have a central place to discuss common business. A tech company might open a shared channel with its advertising agency, for example, or a manufacturer might create one for the contractor that handles its returns. Other good candidates for a shared channel include outside legal counsel and food and beverage vendors, Slack executives told me. “We think of shared channels as the most important thing we’ve launched since Slack itself,” says April Underwood, vice president of product at Slack. “They’re fundamentally a new way of working.”

The shared channels look and feel much like the channels you’re already used to. They can only be created by the administrators of both teams, one of whom must accept the invitation of another. Once the shared channel is created, users can create an unlimited number of public and private interactions. But the interaction is limited to the shared, common space — members of another company’ Slack instance cannot see any of your corporate channels. “We’re not merging data sets in any way that would reveal more than we have to in order to facilitate the exact discussion,” says Paul Rosania, who leads development on Slack’s core product.

In that, they differ from guest accounts, which Slack has offered since shortly after launching in 2014. (Microsoft, which released a rival product named Teams last year, introduced its own version of guest accounts Monday.) Guest accounts were designed with temporary and contract workers in mind, the company says. Shared channels are for ongoing communications between companies, even when the makeup of the individual teams using them changes over time. Slack hopes they will chip away at companies’ use of email, phone calls and other tools that are not Slack.

The company announced shared channels today as part of its Frontiers developer conference, where it also announced some milestones. Slack now has 50,000 paid organizations, comprising 2 million users, putting the company on pace for more than $200 million in annual revenue. That’s more than double last year’s revenue, the company said. Counting free users, more than 6 million people use Slack every day.

The company says it has users in more than 100 countries, and that international users make up 55 percent of its user base. To promote international expansion, the company has invested in localization efforts, and as of today Slack is now available in French, German, and Spanish, with more languages coming soon, starting with Japanese.

If they prove popular, shared channels could offer Slack strategic benefits. A network of companies creating common spaces to communicate is one that paying customers could find hard to leave. Slack’s growing list of rivals may feel pressured to begin building their own version of shared channels, assuming they haven’t already.

“There’s already a network that exist between companies — it’s just not visible to anybody,” Underwood says. “We’ve already had really good networks effects for Slack within a company. We haven’t really had a reason that it matters to one company that another company is using it. With shared channels, this becomes the way of getting work done.”