Team communication apps Slack today is announcing the launch of user groups for teams that pay for premium tiers of service. The feature provides more granularity than the channels for group discussions that existed since the app’s earliest days.

User groups also make onboarding easier. People who join existing user groups can automatically be added to certain channels, Slack wrote in a blog post on the news.

Slack today also released new usage numbers: 1.7 million daily active users and 470,000 paid seats. That’s up from 1.1 million daily active users and 300,000 paid seats four months ago.

That is fast growth. Here’s a chart I made that shows Slack’s daily active users based on publicly available numbers:

Slack daily active users as of October 29, 2015, based on publicly available numbers.

Above: Slack daily active users as of October 29, 2015, based on publicly available numbers.

Image Credit: Jordan Novet/VentureBeat

The growth and the increasing focus on business needs — user groups can hook up to Microsoft Active Directory thanks to integrations with OneLogin, Okta, and Ping Identity — help explain Slack’s $2.8 billion valuation from earlier this year.

Here’s an animated GIF showing the way an admin can send a message to people in user groups:

Slack user groups.

Above: Slack user groups.

Image Credit: Slack

User groups should be working now for companies that pay for Standard and Plus service, according to the blog post.

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