10 million Mastodon accounts

This Sunday marked a major milestone for Mastodon as it reached 10 million registered accounts. Milestones like this are important to acknowledge and celebrate, highlighting the growth of both Mastodon and the fediverse. You may have come across the hourly graphs from the @mastodonusercount account that display the total number of Mastodon users over time.

The 10 million accounts is a good milestone to cheer upon, and worth to be excited about. However, Mastodon's creator, Eugen Rochko, provided more critical commentary by stating his personal statistics indicate closer to 6.5 million accounts. That is a massive difference of almost a third. So what is happening here, how does this difference happen? It’s worth it to dive a bit deeper into. What exactly are we measuring here, and how correct is it?

Different data sources

Doing proper data analysis depends on having proper source data. For a decentralized network getting proper source data can be surprisingly difficult. There is no single definition on how to count an Mastodon account. A simple question of 'do you count accounts on servers that are now offline' does not have a singular answer. This is one of the reasons why different sources show different values for the question of 'how many Mastodon accounts are there?'.

There are three main publicly available data sources that scan the fediverse, and they all show a different value for the total number of Mastodon accounts:

• fediverse.observer (6.9M Mastodon accounts)
• instances.social (10.1M Mastodon accounts)
• the-federation.info (8.7M Mastodon accounts)

As you can see, all three sources provide significantly different numbers for the total amount of Mastodon accounts. The bot Mastodon User Count makes use of the instances.social data, which is the benchmark that everyone used to celebrate the 10M accounts this week.

How reliable is the data

Which data source should you trust, which one is correct? To answer that question depends on your perspective on servers that are not active anymore. It is hard to get a clear answer on the whether the three sources count deactivated servers or not, but there are some clues to help us:

This conversation teaches us two things:

• understanding the account numbers is hard, not even Eugen Rochko, main developer of Mastodon knows for sure.
• The 6.5M that Eugen Rochko names aligns roughly with the 6.9M from fediverse.observer.

This leaves us with a first part of the explanation of the discrepancy between the different values: are deactivated servers taken into account or not. Still, ~3M accounts on servers that are offline seems high. Which servers were so popular and had a ton of accounts that are offline?

The complications do not end here either. There are multiple questions that do not have an easy answer.

• There is 1.5M account difference between instances.social and the-federation.info, with no clear explanation of the difference between the two.
• Making matters more complicated, some servers (mstdn.ca is an example) do show up in the the-federation.info dataset, but not in the instances.social dataset. Considering that the instances.social dataset is 1.5M accounts larger, we would expect the exact opposite. There are probably examples the other direction as well, but I have not been able to find those.
• A post by Greg Clarke shows that instances.social incorrectly shows servers as down, and speculates this might be because of Cloudflare blocking.
• Chris Trottier notes that the instances.social data shows that 242k Mastodon accounts have registered the last week, and asks the question where those accounts actually are. Maybe they are humans, maybe they are bots, but where are they exactly?
• This question is underlined by another bot, which shows every day the top servers with the most new accounts. Here is an example from a few days ago. The data in this daily ranking does not clearly indicate a significant increase in new accounts. This reinforces the question: where are all those new accounts?

It might be clear by now that getting proper statistics is complicated. And this is before we are talking about the Monthly/Daily Active Users. Or the fact that we've only been talking about Mastodon, and not the fediverse at large. For now, we can conclude there is much uncertainty. But that uncertainty does not have to stop us from celebrating a milestone when we get there. Mastodon and the fediverse are clearly growing, and that is the most important thing.