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Despite its marketing, Slack’s free tier limits your total number of users

I recently launched a Slack group for my podcast, the /Filmcast:

I used Slack’s free tier, which lets you view 10K of your team’s most recent messages. After just a few days, we’ve already accumulated about 600 members and even crowdsourced a neat spreadsheet with all their podcast recommendations.

As the group has continued to expand, I’ve started to wonder about what the group’s maximum size could be, so I went looking for whether or not Slack’s free tier had a user limit. I was dismayed to find freecodecamp’s blog post, So Yeah We Tried Slack… and We Deeply Regretted It, which points out that yeah, there is a limit, despite what Slack’s marketing says:

I woke up this morning to a mountain of tweets and emails from new campers saying they weren’t receiving our automatically sent Slack invites. Not exactly what you want to happen three days after your open source community is featured in Wired Magazine.

Slack’s support team was enthusiastic about helping, and kept saying the email notifications had gone out. In my desperation, I tried to manually send out the invites. That’s when I was confronted with an ominous message: “You have reached the maximum number of users”.

My heart sank. Our contributors had sunk so many hours into building Slack features. We’d endorsed Slack to thousands of people on our streams, and even mentioned it in interviews with the media. We were heavily dependent on their service.

In a cold sweat, I started googling. There was literally nothing on web saying anything about Slack having a maximum number of users — only marketing material saying that free tier organizations could have as many users as we wanted. Apparently, we were the first community to ever hit Slack’s undisclosed limit.

Sounds like the service starts struggling at around 5,000 users and poops out completely after 8,500. This is still a pretty healthy number for any community — I think it will be more than sufficient for my needs — but it’s still a limit that Slack’s marketing does nothing to disclose, despite the fact that the above blog post was written more than a year ago.

So, users hoping to build a massive 10K+ sized community on Slack should look elsewhere before investing a ton of resources into this thing (or until they update their marketing to be more clear on how many users they actually allow).

Update: Evidently the limit has been raised since the above articles were published.

Still no word on what the new limit is. I guess there aren’t any communities that invested into Slack’s free tier long enough to find out?