Current breakdown at the time of this post sorted by the number of monthly active users:
- lemmy.world: 101,013 total users / 27,472 active users
- lemmy.ml: 41,972 total users / 4,905 active users
- beehaw.org: 12,270 total users / 4,178 active users
- sh.itjust.works: 17,509 total users / 3,381 active users
- feddit.de: 8,675 total users / 2,935 active users
- lemm.ee: 10,348 total users / 2,751 active users
- lemmynsfw.com: 22,967 total users / 2,310 active users
- lemmy.fmhy.ml: 8,777 total users / 1,704 active users
- lemmy.ca: 5,072 total users / 1,656 active users
- programming.dev: 5,058 total users / 1,242 active users
So the way Lemmy works is that a instance will only know about (and have the content of) a community if a user on that instance is subscribed to it. So when you browse All or search, only those communities that someone on the instance is subscribed to are included in the results. On a smaller instance that’s naturally going to be fewer communities.
Now if you search for a specific community by its URL that the instance doesn’t yet know about, it will actually go and fetch it for the first time. What this looks like to the user though is that the search shows no results, then suddenly 5-10 seconds later the results change and the community appears. Which is not a great UX for someone new. So again on an instance with more people it’s a lot more likely that someone else has already searched for and subscribed to what you’re looking for so that you don’t see that issue