There is an official ICE account on Bluesky.

Bsky is owned by a transphobe, and funded by venture capital. Also from what I've heard they have the ability to ban anyone on any instance of bsky, not just the flagship one, I might be wrong on that one though.

Mastodon has its problems, but there's a scale to it. I personally don't care for the Mastodon software much, my own non-lemmy fedi account is on Friendica, but still.

I'm not some big technical guy, but there is a pretty fundamental difference in how the protocols work. Mastodon uses ActivityPub, Bluesky uses the AT Protocol.

ActivityPub is like email, it's an exchange protocol. So basically you create a link between two accounts by "following" and that says "whenever A posts something, deliver it in this format to B".

ATProto is a bit more complex. It's based around the idea of nodes. A node in this sense is basically a pile of letters. If I decide to post something, that letter gets thrown into the pile with some info like user tags, etc. Another user somewhere else who follows me is in essence just telling their client "pull out all the letters that A has thrown into this pile and shown them to me". And then you have a front facing client that displays the result of that filter in a convenient way. On the one hand, this is why topic lists (I think called collections?) are much easier/better in Bluesky because at the end of the day it's just another filter onto the pile, whereas with an ActivityPub based collection would be a bit more complicated.

In practice what this basically means is that Bluesky is federated in name only. If the Bluesky board decided one day that you couldn't post about cats, but I really wanted to post about cats, I would have to then host the node, the filtering apparatus, and (potentially) the front end. The node hosting specifically is the most technically onerous. If I wanted the Catsky node to federate with the Bluesky node, I would need to set up a tunnel between the two, then posts from Bluesky that the Catsky users would want to see would also be deposited into my node meaning my storage requirements would go up quickly. Conversely, you can run a stable Mastodon instance on a raspberry pi because you only need to be able to store what you want to see, not the entirety of the platform. I personally have only heard of one other successfully hosted node (Blacksky for Black Twitter refugees) and I'm not sure it federates with Bluesky.

In the end, Bluesky works a lot like OG Twitter, which was just a lump of storage and the actual product was the API, but with a couple ropes dangling out the sides with a sign saying "go ahead, hook up, and federate, we don't mind". This is unsurprising as Bluesky and the ATProto were made in essence by the OG Twitter people

Well there are lots of nuanced and technical differences but really the only important part is that 99.9% of BlueSky users are on the "flagship instance", making federation arbitrary.

Further, they have no viable path to profitability, which inevitably eventually leads to exploiting it's users. Meanwhile Mastodon already maintains a non-profit status and already receives more contributions than they need.

Its more like Signal and Matrix. Signal is open source and centralized and Matrix is FOSS and decentralized. Bluesky is supposedly decentralized, but in practice is about as decentralized as WhatsApp which runs on decentralized technology (XMPP).

Choose Mastodon, you are asking this question on its sister platform :)

Bluesky is private, Mastodon is FOSS. Both are federated.

ActivityPub, which Mastodon uses, is genuinely decentralized, and ActivityPub itself is ran by W3C, an international standards organization, while Mastodon is ran by a nonprofit, meanwhile both Bsky and ATproto are ran by a private corporation, ATproto is still semi-centralized, and since ATproto is ran by a private corporation, assuming the VC money runs out and Bsky corporate needs to start to profit somehow to stay afloat, there's nothing stopping them from closed-sourcing ATproto (as rugpulling of this sort is legal in permissive licenses like what ATproto is licensed under) and starting to either push ads in it, paywall certain features of it, or both, for example.

Blacksky actually managed to completely split itself off from Bsky corporate infrastructure, but what if Bsky corporate gets hostile against that?

they both use decentralizable tech, but in practice only mastodon is decentralized

I would say the defining difference is that bluesky is not effectively a decentralized service. Federated(decentralized) social media platforms are great because it's hard for one single company or organization to censor the entire network.

For mastodon there are some big servers but all the uses are still quite distributed. For bluesky basically all users are registered on a central server run by the company bluesky, which has sole control over what's allowed and what's not. This has already been used by them to censor political content.

In theory blue sky is capable of being kinda decentralized but not really and even if you were to host your own account, they would still be able to censor you.

So in simple terms it comes down to:

• Bluesky is just another twitter that will eventually go to shit like every other network (and arguably already has)
• Mastodon is here to stay and while it might be small by comparison, it will never really die or be controlled by some central entity

The problem with Mastodon (ActivityPub) is that your identity is held hostage by your server admin. If your instance goes down or you have a disagreement with the mod, good luck moving. You can migrate followers, but you lose all your posts and history.

ATProto fixes this by decoupling your identity from the server, you can swap servers without losing anything.

Also, Bluesky has truly customizable algorithms instead of being forced into the chronological view or whatever the instance admin decided.

Seeing quite a bit of disinformation about bluesky and the ATprotocol here.

In short, ActivityPub work more like emails while ATproto works more like old-school websites and indexers

This might be a bit technical, but basically, your bluesky data lives on a PDS which is a lightweight database of all your data/interactions on the network. The PDS are decentralised and self-hostable. All of the data from all the PDSes are aggregated by relays. Anyone can host their own relay. They are even technically not required. Then there are the AppViews that ingest data from the relays in real time and do stuff like caching and providing an app-specific conveinient api. Bluesky is an appview. It consumes the data from all PDSes and filters on bluesky-specific data. Other AppViews like Leaflet and Tangled use the same protocol and infra, but focus on their own data.

Here is a long form article that explains it in even more details. https://overreacted.io/open-social/

I'm on both. If you only want to follow techies, go with Mastodon. If you want to follow non-techies or celebrities or whatever, go with Bluesky.