Sam Altman says this is his most-used app — and it's not ChatGPT

• The most-used app on OpenAI CEO Sam Altman's phone isn't ChatGPT.
• It's actually Slack, which he says he's on "all day," with iMessage being a close second.

Sam Altman and Bill Gates discussed their phone habits in a recent episode of Gates' podcast, and it turns out messaging apps are king for the two tech titans.

The pair talked about the most-used apps on their phones in an episode of Gates' "Unconfuse Me," released Thursday. For Altman, that's Slack, which he says he uses "all day" and "way more than email."

"I wish I could say ChatGPT," Altman joked. A close second for him is iMessage, he added.

This may remind some of you of the funny revelation that OpenAI employees use Google Meet instead of Teams, even though Microsoft has poured $10 billion into their company.

As for Microsoft founder Gates, he's most frequently using Outlook.

"I'm this old-style email guy," he said. "Either that or the browser because, of course, a lot of my news is coming through the browser."

On that topic, Altman said, "I didn't quite count the browser as an app. It's possible I use it more, but I still would bet Slack. I'm on Slack all day."

Altman and Gates also discussed their concerns about AI on the podcast, with Altman saying he worries about how quickly people will have to adjust to AI transformations in the ways they live and work.

"Each technological revolution has gotten faster, and this will be the fastest by far, and that's the part that I find potentially a little scary is just the speed with which society is going to have to adapt and that the labor market will change," he said.

Altman briefly touched on his short-lived ouster from OpenAI as well.

Altman was fired from OpenAI in November, when the board at the time said they'd lost "confidence in his ability" to lead and that he was "not consistently candid in his communications."

After Microsoft poached him to lead a new AI research unit and the vast majority of OpenAI employees said they'd quit and follow him unless he was reinstated, Altman was brought back less than a week after his shock dismissal.

"A lot of people have remarked on the fact that the team has never felt more productive or more optimistic or better," he told Gates. "And so I guess that's like the silver lining of all of this. In some sense, this was like a real moment of growing up for us. We are very motivated to become better and to become a company ready for the challenges in front of us."