Mastodon: servers, good and bad

Sunday 27 November 2022

Like many people these days, I’m looking around at alternatives to Twitter, and Mastodon is a clear favorite. Comparing the two, the big differences, both good and bad, come down to servers.

Twitter is one web site, run by one corporation. This is easy to understand, and makes it easy to find lots of people, but has the disadvantage that a deranged over-leveraged misanthropic moron can buy it and make it terrible.

Mastodon is both a web application and a galaxy of tens of thousands of separate servers running that software. Each server is run by a different person (or team), each with their own idea of what the server is for, and how it should be run. The servers are not isolated islands, they are federated together: they communicate with each other so that people on one server can see the posts from other servers.

This is the big difference between Twitter (centralized) and Mastodon (distributed and federated), and it plays out in both good and bad ways. I’m new to Mastodon, so take all this with a grain of salt. Some of what I label as bad is due to growing pains and can be improved over time. Some is essential: distributed grass-roots organization is messy and requires work. But it doesn’t suffer from Twitter’s current problem, so it’s worth working at.

Here are my impressions of the pros and cons of distributed federation:

Initial hurdles (Bad) When you try to join Mastodon, you are immediately asked to choose a server. This is not an easy decision. Coming from a centralized service like Twitter (or Facebook, YouTube, Reddit, etc, etc), the question makes no sense. The list of servers to choose from is a tiny fraction of all the ones out there, and they seem to be very strange niche communities. The implications of the choice are not obvious either: how will it affect my Mastodon experience, and can I change my mind later? The choice cannot be avoided, you need to pick a server to be on. But over time, Mastodon can make the choice easier.

Independence (Good) Because there are many servers, Mastodon can’t be bought by a crazed billionaire. There is no company, no centralized thing that can suddenly change hands. If part of the galaxy goes in a bad direction, the rest of the servers are unaffected.

Moderation (Mixed) Moderation is handled on each server by the server admins. This is good: you can join a server with a moderation policy you approve of. But it also means that server operators have to handle this delicate and complicated job. It might become a chore they don’t want to do, or can’t do because of volume or shifting interests. A well-moderated server could slide into disrepair.

Server as community (Mixed) One philosophy of server choice is that a server will be for a certain community. There are knitting servers and pet-lover servers, liberal servers and conservative servers, and so on. This can be a good way to cluster together with people you have an especially tight bond with. But most people are not members of a single community. I live in Boston, make software, like math, and am a parent. Which of those community identities should I use to choose a server? I don’t have to use any of them. Not all servers are organized around a topic at all. No matter what server you choose, you are not limited to just one topic. On the other hand, some servers are so topic-focused that they might consider some posts offensive that other servers see as perfectly normal. Some aspects of Mastodon’s design and culture grew from this idea of “server as community,” like the Local Timeline, which is posts by anyone on your server. As Mastodon attracts more people, the value and feasibility of those aspects are weakening.

Re-centralization (Bad) As people join Mastodon, there’s a natural tendency to avoid the question of choosing a server by joining what appear to be the “default servers.” This leads to over-sized servers that don’t fit well with the original design of Mastodon and can lead to problems. Right now, the largest servers are closed to new accounts, pushing people to spread out more, which is good.

Defederation (Mixed) A server can decide to never communicate with some other specific server. Your vegan community server could decide not to federate with the safari hunter community server, because of the clash of interests. That’s good, it helps focus you on what you want to see and keeps communities cohesive. It gives server admins a giant kill switch to keep their servers safe. The downside is that one malicious user on a large server could cause other admins to defederate that entire server, and now all of that servers’ users are invisible to you. Wholesale defederation is frowned upon and a last resort, but as small-server moderators try to handle the growth of Mastodon, it could happen more, and you have little say over it.

Incomplete visibility (Bad) Federation is not total: there will always be posts that you cannot see. Roughly speaking, you can see posts by anyone on your server, and by anyone on the home server of any person followed by people on your server. This will be a lot of posts, but it will never be complete.

Server turnover (Bad) Your server could go away. Many servers are run by people because it seemed like an interesting thing to do. Maybe their interests shift. Maybe their server attracted more people than they were willing to support, either in infrastructure costs and effort, or in moderation effort. The server could stop operating, or could just silently wither. It could even be purchased by an egomaniacal tyrant. But it would only be one server, and you can choose a new server and move to it, bringing along your followers.

Open source (Mostly Good) Mastodon software is open source, which means it is safe from takeover, because anyone can take a copy of the software and extend it if they need to. It also means that many people can help improve it, although open source can sometimes be weak on the processes for how to decide what changes to make. A downside is that different servers can be running different versions of the same software, or can be running different forks of the software, so there can be differences between them in what they support and how they work.

Funding (Mixed) Because there is no central company, every server admin has to fund their own server, both the technical infrastructure, and the time they put into it. This can be difficult, and given the recent surge of interest, unpredictable. Some servers ask for donations, some even charge money to join. The good news is there are no ads (yet?), but you might need to chip in a few dollars to keep your server going. The good news is that you can choose who to give your money to.

Following and liking (Bad) When you see a post in Mastodon, it is easy to follow the author: there’s a Follow button just like on Twitter. You can also favorite (like) their post easily. But if someone sends you a link to a Mastodon post, you will be visiting that post’s server instead of your own. You won’t be logged in there, because you have an account on your own server, but not on any others. Then following the author or liking the post is more difficult: you have to copy a URL and paste it into the search box on your own Mastodon. This makes off-Mastodon discovery of new people harder.

User names (Bad) Your handle on Mastodon is more complicated than on Twitter, because you need to name your server also. I am It’s more to remember than just @nedbat on Twitter, and it doesn’t fit as well in places like the footer of presentations. Also, someone else can take, and there’s nothing I can do about it.

ActivityPub (Good) The rabbit-hole goes deeper: Mastodon is just one application built on a standard protocol called ActivityPub. Other services can also implement it, and be part of the universe of federated applications known as the Fediverse. Tumblr has announced they will support it, so you could see many services all mingling together.

•    •    •

So, what to make of all this? Twitter seems on a bad track, and it’s hard to imagine any new centralized social network gaining Twitter-scale adoption. Mastodon is harder than Twitter, but has its advantages. Decentralization is messy, and while authoritarian centralized services are simpler to understand, they offer little freedom, and bring great risk.

But as Dan Sinker said:

*whispers* Most people don’t care about decentralization and governance models, they just want someplace to hang out that’s not a hassle.

Twitter was never going to last forever. I don’t know if Mastodon will grow to anything close to its size, or what else might. But it’s interesting to watch the evolution and try it out.



On the other hand, some servers are so topic-focused that they might consider some posts offensive that other servers see as perfectly normal.

This hasn’t been my experience, but I’m super curious where this comes from. I’ve seen highly topical servers, but usually those don’t federate with the wider network.

Generally, if your server has a local and federated timeline, it’s understood that people can post whatever they want even if it’s “Off topic”. I use - a server devoted to retrocompuitng, but I assure you people post about all kinds of things :)

Overall though this is a thoughtful, well written and very even handed piece and doesn’t fall into some of the FUD talking points I’ve seen floating around. Thank you for writing it!


I love the idea of Mastodon because it’s a return to the diverse and sometimes weird Internet I knew.

However I don’t get it how the “terrible Twitter” would look like and how that would not happen with Mastodon.

Twitter it’s already useless if you read the open feed instead of only who you follow, so… more ads? What’s the doomsday scenario here?

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