There are tens of thousands of Fediverse servers with millions of users in total, and this amount is growing all the time. There are hundreds of millions of posts going back almost a decade.
However, each server only “notices” posts and profiles that are connected to its members in someway, either through an interaction, or a following, or various other specific situations.
The reason why servers only notice certain posts and profiles is because would be horrifically expensive for every independent server to keep a complete, up-to-date record of every post ever made by every user on every server in all languages. The only people who could afford such a comprehensive system would be megacorporations like Facebook, Google, Twitter etc.
The whole point of the Fediverse is to allow small independent servers to exist as part of a larger network, so that the network is as spread out as possible (click here to find out why this is a good idea). The smallest Fedi server starts from about US$10 a month to run, and this low cost is possible because the server only needs to display posts and shares from people its users follow. Even the largest Fediverse servers are able to operate on a fraction of the budget of a commercial social network because they are only showing posts their users have to see. (If you’re interested, there’s a complete list of what a server can see here.)
So, what are the downsides of not having all posts from every server visible everywhere?
If you discover an account that no one on your server has followed or interacted with, it may look totally blank even if it has posted lots of times. This can mislead people into thinking a profile is inactive and not worth following. If you follow a profile you will start seeing all its posts published from that moment onwards, but older posts are not loaded retrospectively.
Also, searches will produce fewer results and threads may look less complete if your server hasn’t noticed accounts related to the topics you searched for.
Couldn’t Mastodon at least show a few old posts instead of blank profiles?
Yes, this is a good point. One of the main shortcomings on Mastodon and many other Fediverse server types is the lack of “backfilling”.
Backfilling is when an account’s posts are automatically fetched to your server when you follow or view an account’s profile. Without backfilling, profiles can look blank if no one on your server has followed it before. At the moment, the only posts backfilled by Mastodon are pinned posts.
The main thing preventing backfilling from being used has been concern about stress on servers, especially if an account has thousands of past posts to backfill. A possible compromise might be letting servers decide for themselves if they will allow backfilling, and how many posts they are willing to backfill.
If you’re comfortable using Github, you can let the developers of Mastodon know you want some kind of backfilling to be implemented by giving a thumbs up on the relevant issue ⧉, and if you have your own ideas you can contribute to the thread.
Is there any way to get round the problem of search results and threads?
Yes! If you’re an ordinary user you can follow and post to groups, which distribute all of their content to everyone in the group no matter which server they are on.
If you’re a server admin, there are ways you can get more results visible on your server, even if your server is small and new.
How about just having everyone on one huge server?
Well, you could do this, but then you end up back where you started with a server that can be easily bought out by Elon Musk or whoever as soon as it gets popular. It would be entirely missing the point of the Fediverse.
How about having one giant relay server?
Again, you couuld do this, but then whoever controls that giant relay server would have an unusually large amount of power over what is visible on the Fediverse. It would also be expensive to run. Combining massive expense with centralisation makes it very likely that such a relay server would end up being sold to the highest bidder and start going down the path of “enshittification ⧉“.
Do any Fediverse server types use backfilling right now?
Yes! PeerTube automatically backfills all of an account’s videos as soon as an account is followed from a PeerTube server, even if the videos are very old. This works fine, and shows that backfilling can be done on the Fediverse.
Also, as mentioned above, Mastodon does backfill pinned posts already.