You probably haven’t heard of an online game called Glitch. It existed for only a little while before the company that built it, Tiny Speck, closed it down in 2013. And yet we have Glitch to thank for a tool that is changing how people in many organizations get their work done.

When they were developing Glitch, Tiny Speck’s employees were scattered between San Francisco, New York, and Vancouver. To make it easier to communicate, the team created an instant-messaging program that could serve as a hub for everything they were doing. It archived messages, just as you’d expect in e-mail, but it also made it possible to see and search information from other business applications, from Dropbox to the corporate accounting system. Soon they realized that this application, now known as Slack, was potentially useful to any organization and could be a far bigger opportunity than Glitch. After some of the fastest growth ever seen in business software, Slack now has over 1 million users each day, and the company that has come together to develop it is valued at nearly $3 billion. It’s a member of this year’s 50 Smartest Companies list.

Slack is headed by Stewart Butterfield, who cofounded the photo-sharing site Flickr and sold it to Yahoo in 2005 for more than $20 million. He told MIT Technology Review’s senior editor for mobile, Rachel Metz, that he hopes Slack will do for all companies what it did for his: free people up to get more work done.

There are many communication apps for work that offer aspects of what people can do with Slack. How is Slack different?

Usually within a single organization there will be many, many different means of communication. There’s this huge value in bringing all those together. So if you can provide a tool that works for both ends of the spectrum—like “I’m going to be five minutes late to the meeting” but also “Here’s an important change to our benefits policy that all employees must be made aware of, and you have until June 30 to file some form,” or something like that—if it works for all of those and all the use cases in between those, then it will either consolidate or replace many other forms of communication. The fact that there’s only one place, one tool that you have to check, one record of all the conversations, and the fact that it’s searchable, makes a huge difference.

I’ve heard of not just companies using Slack but classroom teachers as well.

We hear of people using it with their family. I have heard of a couple using it.

Despite its popularity, you’ve told me in the past, perhaps somewhat tongue in cheek, that Slack is “just a giant piece of shit.” Is it still?

I think we’ve made some improvements since then, but on the whole there are still so many problems. There are a lot of things that are still shockingly bad. Amazingly, you actually cannot invite people from the mobile app if you’ve just created a team. It’s just not possible. And that’s insane. It’s inconvenient for people, obviously, and frustrating because people just assume, “I have this brand-new messaging app on my phone—how do I invite people?” And they’ll try every single thing through the whole app. It’s also incredibly stupid for us as a business, right?

Assuming you can fix that, what’s a feature you’d want to add that is impractical or technologically impossible for now?

Automatic summarization of what happened while you were away. It sounds very simple in one sense. But doing it right will be very difficult. If I said to Bob or Amy, “Go read all of the messages that came in over the course of the day that I haven’t looked at yet and tell me the three most important things that I need to deal with right away,” it would be very easy for them to do that, whereas asking a computer to do that is impossible. So that’s something we’re very interested in—especially not just the ability to do it in a one-off way but also, ideally, the ability to learn from me about what I think is important and the way in which I would like it presented.

Slack has a free service, but you charge for some features. How big a business can this become?

What we’re doing now is an amazing business. In [software as a service] businesses, the benchmark for churn [loss of customers] is typically 1 percent a month—that’s kind of the boundary between good and maybe starting to be dangerous. Anything over 1 percent starts to be worrying. We’re not even at a tenth of a percent per month. Essentially, no one ever stops paying us once they start paying us.