Mastodon Growth Numbers Might Not Mean What You Think They Mean

Mastodon’s growth in the last month has been extraordinarily fast – but just how fast? Did the number of users jump up to 2.5 million or 8 million in the month or so since Musk took over Twitter? Both those numbers for current users are swirling around, especially the 8-million one, because it’s coming from a popular bot account – the same bot that’s the source of a viral chart showing waves of Mastodon growth in response to events at Twitter.

The vast difference between 2.5 and 8 million isn’t just because the first is a tally of active users – accounts that have at least been logged into in the last month – and the second is the number of existing accounts. The data sources are measuring very different “Mastodons.” And the numbers that are up around 8 million don’t really represent the Mastodon network that most of us are in.

There are other data sources, too, and their tallies are different again. Those with the highest counts are so high because they include websites that could technically interoperate with the core Mastodon network, but they don’t fully, or at all. Many of those websites are the home bases for spam, trolling, and hate speech, though that’s not the whole picture of what I’ll call “off network”.

I’ll walk through this in detail below, including data sources, and why Mastodon statistics aren’t straightforward. But I’ll start with an overview of the Mastodon network we’re joining based on the most official data. It’s probably something of an under-count, but I think it’s the most accurate depiction we have of the network we’ve joined.

• When Musk took over Twitter, there were 3.6 million accounts in the Mastodon network. That includes people with multiple accounts and bot accounts. But even though they’re not unique individuals, accounts are called users (the same as at Twitter).
• Before the takeover, only about 10% of those Mastodon accounts had been used in the previous month. Or to put it another way, 90% of Mastodon accounts weren’t active. Since then, 1.8 million accounts have been added, bringing the total to 5.4 million accounts – and close to half of all Mastodon accounts had been at least logged into in the last month (47%). That added up to 2.5 million active users in the first days of December.
• The percentage of active accounts has just dropped slightly. We’re starting to see the impact of people who opened accounts right after the takeover at the end of October, and haven’t logged back in. Some of the people who had joined much earlier – Mastodon started in 2016 – are still becoming active again.
• The number of new accounts is still growing. However, there have been lulls between waves of newcomers after events at Twitter. There’s a lull now. The mean number of new accounts per day in the week up to December 2 is about 12,000. The highest peak so far was in November with over 134,000 new accounts on each of 2 consecutive days.
• The nodes in the Mastodon network are websites, usually called instances or servers. They can have anything from a single account to hundreds of thousands. Instances being added to the network is the main way that Mastodon can scale.
• In the month or so since the big Twitter migration began, the number of instances has been fluctuating, with many new ones, and others folding. The total has grown from over 3,300 “before”, to just over 8,400 by December 2.
• The sources tallying up 8 million users are not a full picture of the “off network” Mastodon instances. But within that 8 million are 2.6 million “off network” accounts – that’s much smaller than the number of accounts within the network. In the current comparative lull, however, “off network” Mastodon is growing accounts faster than the Mastodon network. This might include new instances that will be joining the network, but I don’t know.
• We still don’t have a good sense of how many Mastodon accounts are just there as people’s backup plans, and how many people are going to stay active, regardless of what happens at Twitter.

[Update December 17, 2022] On December 16, after multiple journalists were banned/suspended from Twitter, there was a wave of journalists and others to join Mastodon. It wasn’t the biggest wave by a long way, but it led to a major landmark: The number of posts in day surged past half a billion for the first time – from 466m to 568m. Mastodon post with links to data here.

So let’s unpack this, starting with what we mean by “Mastodon”. There isn’t a single “Mastodon”, in the way there’s just the one Twitter. A Mastodon instance can be set up for a single person, or for others to join.

An instance can then stand alone, for communication among its members only. The group could have a walled-off instance because they don’t want to join the network – or because the network refuses to have anything to do with them. Many instances let loose spam, trolling, harassment, or denial-of-service attacks on “Mastodon” users. As that emerges, “Mastodon” instances can limit (silence) or suspend (block) the instance. That can cascade through the network. Instances can also silence or suspend any other instance without adequate or compatible moderation practices to their own, as a prevention strategy.

All this means that for many of us in Mastodon, the size of “our” Mastodon varies, on any given day. And that’s not just because people are opening and closing accounts – it’s because the number of instances whose posts we can see, and that can see ours, can be shifting. The concept of “Mastodon” is pretty fluid.

A person in an instance with looser moderation might be in a bigger Mastodon than a person in an instance that’s going high-throttle on protecting their community from trolling and harassment. Furthermore, each of us can block instances for ourselves.

So what do I mean when I talk about the Mastodon network and its “official” data? It’s the instances networked around the core of Mastodon software, and its founder in Germany. It’s what you see when you go to joinmastodon.org. The instances listed there have all signed up to do the following:

…adopt the Mastodon Server Covenant, meaning that they pledge to actively moderate against hate speech, to take daily backups, to have at least one emergency admin, and to provide at least 3 months advance notice in case of shutdown.

Mastodon documentation

The 2.5 million number comes from that Mastodon network. It’s the first of the 4 major sources in the table below, ordered from the lowest account tally to the highest. I used that first source for the summary above. The second is the data source I used in my post last month before I learned about the first one – the tallies between these 2 are roughly similar.

Comparable Mastodon statistics from several sources

Before = October 27, 2022 (before Musk’s takeover of Twitter)

After = December 2

* Date before: presumably end of October; Date after; December 4

Key	Source	Instances (Before)	Instances (Now)	Accounts (Before)	Accounts (Now)	Active users (Before)	Active users (Now)
1	Official Mastodon API (See recent charts using this, by Tobia Alberti)	2,874	8,401	3.6m	5.4m	370,360	2.5m
2	Mastodon help (Posted each day, I gather the data manually)	3,676	10,794	3.4m	5.6m	328,293	2.7m
3	Fediverse Observer (Poduptime on gitlab) (API)	4,940*	12,351*	3.7m	6.9m	n.a.	n.a.
4	mastodonusercount bot (gallizoltan on github) Data source: instances.social (API) (Also the source for observablehq.com data.)	n.a.	n.a.	5.6m	8.0m	n.a.	n.a.

The second 2 sources are counting a lot more servers. They’re both opt-in collections, and they both end up with a very high tally of accounts. The last one is the source for the 8 million and that bot I talked about earlier. It’s from instances.social, a website with a wizard for finding Mastodon servers. The Mastodon network explicitly does not draw from this list, although they used to. The reason? “[I]t simply listed every instance submitted – regardless of stability or their code of conduct.”

Here’s an easy example of how this plays out. There’s an instance called FreeSpeechExtremist, that has a policy of never blocking any instance. At Mastodon.social, which is one of the pair of large instances run by Mastodon’s founder, FreeSpeechExtremist has been suspended for hate speech. (You can’t always see an instance’s “block” list, but there’s a sub-section called “Moderated servers” under “About” at instances’ homepage which often shows them.) Both sources 3 and 4 in the table include FreeSpeechExtremist. It’s not part of the Mastodon we’ll encounter through our network accounts though.

I couldn’t find a list of the 8,000+ servers being counted in the official data – again, if you know where one is, I’d love to see it. But I bet suspended instances like FreeSpeechExtremist aren’t there. From digging around in the data sources, I think that commonly limited instances aren’t being included either. If that’s right, a single instance explains a lot of the gap between 5.4 million accounts and 8 million.

It’s a Japanese one, called Pawoo.net. It has almost 790,000 users, making it the second biggest Mastodon instance after Mastodon.social. There was a time it was the biggest, and more than one Japanese instance overtook Mastodon.social. Now, though, it has been “limited”, or silenced to us. You can read about it here in brief, and here in a long look at the events surrounding the schism. Pawoo, like several other large instances in Mastodon’s history, was created when a community was booted out of Twitter. Here, both that and its exclusion from full participation in the Mastodon network, are because of a culture clash around a popular form of Japanese art. (It depicts young girl manga/anime characters in ways regarded as child pornography in other countries.)

In real terms, that huge instance isn’t part of the Mastodon we’ve joined. Nor are all the spam, troll, and hate speech mills the moderators play whack-a-mole with to protect the Mastodon network. Because that 8 million figure reflects neither the network we’re navigating nor the full off-network Mastodon and relevant Fediverse (federated universe), I think it’s an interesting, but inherently misleading, data source.

I haven’t yet found a way to keep up with the official data in as user-friendly a way as the instances.social-derived bot. Tobia Alberti might be updating her charts once a week. (Note: I’ve had some instability with that spreadsheet in Google Chrome, but it worked with other browsers.) I’m gathering data manually, and still hoping someone else knows of an accessible bot, or will create one (hint! hint!). You can check out the day’s official tally of monthly active users and instances (servers) here.

In the meantime, I think it’s gotten to the point that it’s better to ignore the data from the bot if you can. At the moment, it’s telling us that we’re in a period of high growth, when in fact, we’re in a lull. I think you’ll know it quickly if/when another big wave hits. For the last few, you knew it was happening because the website slowed down so much before capacity increased to absorb the added load of newcomers. And at the same time, your timeline was full of #Introduction posts, which was lovely!

How long might this lull last? Who knows what’s going to happen next, especially when $8 blue check 2.0 rolls out any day now. If you’re thinking of setting up a Mastodon account, do it now: It’s much easier during a lull!

A few days ago, I posted about why I finally left Twitter. I quoted Jelani Cobb’s excellent article on why he quit. He pointed out that Musk is trying to profiteer from an information war, and basically “selling weapons to both sides.” The terms of the battle, Cobb pointed out, are set by him and he wins “by having the conflict drag on endlessly.” No one knows how many more mass-joining waves there might be at Mastodon. It seems more likely than not that there’ll be quite a few of them.

I’m @hildabast@mastodon.online at Mastodon. You can keep up with my work at my newsletter, Living With Evidence.

This is the fifth post I have written on the Twitter/Mastodon migration. Future posts on this subject at this blog will be tagged Mastodon. And the previous 4 are:

1. On November 3, 2022, at Living With Evidence: Shuffling Communities and Twitter Migration.
2. On November 13, here on Absolutely Maybe: Mapping the Mastodon Migration: Is It a One-Way Trip or an Each-Way Bet for Science Twitter?
3. On December 1, here on Absolutely Maybe: Reflecting on Twitter, White Flight, & “Quote Tweet” Tensions at Mastodon.
4. On December 2, at Living With Evidence: The Relief of Leaving Twitter.

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Disclosure: I joined Twitter in October 2010, and Mastodon in October 2022. At the time of writing this post, I had just under 3,000 followers at Mastodon (growing), and over 31,000 at Twitter (dropping).

Acknowledgements: I’m grateful to Nemobis and David Hood for helpful pointers as I’ve been trying to get my head around Mastodon data sources. I learned about the “core” Mastodon API via Micah Lee’s Mastodon timeline, and about Tobia Alberti’s charts of that data as well. (And my thanks, too, to Martin Vermeer, for spotting an error in numbering of the sources in the original: Fixed soon after posting.)

The image at the head of this post is public domain. It includes a data chart of mine, and a public domain Mastodon mascot via Wikimedia Commons.