Mastodon is specialising in microblogging and, most importantly, interaction between single user accounts. It has absolutely no support for groups whatsoever.

Lemmy, in turn, is specialising in groups. And it has even less support for interaction between single users.

Mastodon users can theoretically subscribe to Lemmy communities. To them and to Mastodon, however, it’s like following a user. Lemmy requires a title for each new post which aren’t implemented in Mastodon (except for inbound Article-type objects).

Also, Mastodon has no support whatsoever for enclosed threaded conversations with exactly one post and otherwise comments. On Mastodon, everything is a post, and you have to jump through hoops to see an entire thread. If you want to reply to a post, and you want everyone in the thread to see your reply, you have to mention absolutely everyone who has participated in the thread so far.

Well, and then there are mentions which Mastodon automatically adds to replies, but which are unnecessary on Lemmy, as well as hashtags which are critically important for content discovery on Mastodon but entirely unsupported by Lemmy.

The other way around works even less because it’s absolutely impossible for Lemmy users to follow Mastodon accounts.

Part of this mess are development politics. The Lemmy devs aren’t even interested in properly federating with Mbin and PieFed, much less anything else that has groups and even less anything that doesn’t. Gargron’s goal has always been to make Mastodon appear to be the Fediverse proper, i.e. the Fediverse being a “decentralised walled garden” that only consists of Mastodon. And even if a Mastodon user was to stumble upon the non-Mastodon Fediverse, it was to look broken and inferior in comparison with Mastodon.

Be careful—you’re getting a few things mixed up.

Lemmy is software built around the concept of “communities.” A Lemmy user isn’t focused on what individual users write; rather, they are interested in what is being posted within the specific communities that interest them!

Therefore, it makes perfect sense that you wouldn’t see content from Mastodon users if they haven’t consented to being visible to you.

In fact, if a Mastodon user chooses (via opt-out) to post within a Lemmy community, you will see that content—provided that you are also subscribed to that community.

Conversely, a Mastodon user will generally see your content in the following three scenarios:

1. If they follow you, or if they follow someone who follows you.
2. If they follow someone who “reposts” (or “retweets”) your content.
3. If someone on your instance follows you, or follows someone who “reposts” your content.

Note that when I say “someone who reposts your content,” that “someone” could be another Mastodon user, but it could also be the Lemmy community where you are posting. In effect, these communities function as special ActivityPub users; Mastodon perceives them as such—for instance, the community https://lemmy.world/c/fediverse appears to Mastodon as the user @fediverse@lemmy.world.

Bridging the “social-verse” (social networks) and the “forum-verse” (discussion forums) has always been an important goal for me. I’ve made an effort to inform Mastodon users about this through posts like this one: https://www.informapirata.it/2024/01/02/mastodon-tips-how-to-use-friendica-groups-forums-and-lemmy-communities/

…but it’s clear that Mastodon users—and, more importantly, Mastodon administrators—aren’t particularly interested in connecting their users with communities on platforms like Lemmy, PieFed, MBin, or NodeBB. Fortunately, there are some positive developments on the social side:

• There is an app for Mastodon called “Raccoon for Friendica” that makes managing groups easier for Mastodon users. (It’s called “Raccoon for Friendica” because it originated for Friendica, but more importantly, its developer previously worked on an app for Lemmy.)
• A fork of Misskey called “Catodon” offers excellent support for ActivityPub groups, potentially ushering in a new era that bridges the “socialverse” and the “forumverse.”

There are also interesting updates on the forum side: NodeBB now allows administrators to forcibly “move” initial posts into a specific category (in NodeBB, “communities” are referred to as “categories,” but they still function as ActivityPub groups). While this move isn’t visible to other instances within the “forumverse” (such as Lemmy or other NodeBB instances), it is visible to “social” users—because the “category” effectively “boosts” the moved post, allowing social users who follow that community to see it.

I’m not familiar with Piefed, but it would be great if the Lemmy developers took two steps:

1. Introduce a feature similar to NodeBB’s, allowing posts to be moved within a community.
2. Find a way to make this move “visible” across the board—so that it’s not just users on the local instance or those on social platforms who see the change, but also users on other “forum” instances!

However, there could also be negative developments. The most likely risk, in my view, is that the “little dictator” (Mastodon) might decide to implement ActivityPub groups in its own idiosyncratic way—one that is, predictably, incompatible with the “forumverse.” Given how they implemented “quote-retweets,” I’d say that bad news is more likely than good news…

My thoughts:

On Mastodon people follow users, and on Lemmy people follow topics so I spend more time on Lemmy, but do see some of the same posts on both. I think the cocktails would do well on there but would have no idea how to accomplish a cross posting situation, nor would I feel comfortable posting other people’s posts without asking each time. And I don’t really want people following me.

We do need more cross functionality, plus we need instances with a clear set of rules enforced equally ending in a jury trial of users for major violations, rather than the feudal system we have.

We will never catch on as it now stands. 40k weekly users on lemmy is it?

Try Mbin or PieFed, they got you covered. I think especially MBin is great to be part of both of these continents of the Fediverse world. PieFed is still missing some bits as of now.

While I do agree that not all platforms show all content, I would rather put the blame it on Mastodon, which decided to do whatever it wants and not invest in ActivityPub, only use it for its own benefit. I’m not surprised other platforms went the same way, although it is incredibly saddenin.

This seem to stem from a misunderstanding. Lemmy and Mastodon have different goals. Users of each generally don’t want the other’s content generally showing up en masse.

If you want to see something from Mastodon, you can usually get it on Lemmy, and vice versa. I don’t often see Mastodon posts either, but that’s because I only follow Lemmy communities, so I only see them when someone on Mastodon tags a Lemmy community in their post. If you want to see more Mastodon content, see if you can follow some users or hashtags from Lemmy.

But that might not be supported; I haven’t tried. If you prefer Mastodon, I’m pretty sure that you can follow Lemmy communities from there.

My Mastodon feed is full of Lemmy posts, the reverse is less true.

That doesn’t really change the fact that they aren’t identical use-cases.

Not so sure, i could subscribe from my Piefed account to Peertube channels, and get their videos in my feed. Im pretty sure it works from Lemmy too. And it feels like the Fediverse in action to me !

lemmy and mastodon are more than just activitypub frontends. mastodon is for microblogging where you follow users while lemmy and other threadiverse software is a discussion forum and news aggregator where you follow communities. it’s cool you can share some posts across these platforms but there is a reason you don’t see the same posts everywhere and that’s a good thing.

Piefed introduced following Mastodon users a few months ago: https://join.piefed.social/2026/07/03/piefed-v1-7-is-released-following-users-faster-browsing-smarter-moderation/

Not every message the activitypub can send is suitable for every platform. Reddit style discussions just don’t map to Mastodon.

The most important thing is that lemmy, Mbin, piefed, etc. can communicate freely. You can try to build a platform that does it all but I think it will be messy.

It’s quite trivial to follow a Lemmy community or user.from Mastodon. Then it’s just on your feed like normal. To post a new thread from Mastodon you just @ mention the community. On oirFed you can hashtag your post, too.

It’s really following Mastodon from Lemmy that’s a challenge. As there’s no mechanism to follow users or hashtags here.

I remember Mastodon was working on groups so I imagine interaction from Mastodon to Lemmy would improve. Bonfire is rolling out groups pretty soon it seems. I’ve been trying it for a while now and I access both microblogs and groups from Bonfire.

likewise, i’ve rarely if ever seen a post from lemmy on mastodon. these two platforms just don’t seem to interact much. the fediverse is already very small. fragmenting it even further by having multiple services that basically don’t talk to each other is not good

I think part of this is the initial desire to model Fediverse platforms after mainstream counterparts. So you have Instagram-but-federated, Twitter-but-federated, Reddit-but-federated, YouTube-but-federated, TikTok-but-federated. These platforms don’t really interact with each other directly, so the Fediverse ended up modeling that incompatibility, too.

That’s the area projects like Mbin and Bonfire seem to be better at.

I sometimes see my own Lemmy posts, and often others’, on Mastodon, but I have no idea how it happens: It seems random, and I’m not the one doing it…