Mastodon vs Bluesky: Differences and Which to Pick

Pick Mastodon if you want a community on a server whose rules you choose, run by a non-profit project. Pick Bluesky if you want something that feels like early Twitter, with one sign-up and custom feeds.

Both are open networks, but they run on different protocols, so accounts on one cannot follow accounts on the other by default.

Mastodon vs Bluesky at a glance

Mastodon is a federation of independent servers on ActivityPub. Bluesky is one large network on the AT Protocol, built by a for-profit company. The table covers the differences you notice in daily use.

	Mastodon	Bluesky
Protocol	ActivityPub	AT Protocol
Who builds it	A non-profit	Bluesky PBLLC, a for-profit company
Where your account lives	On a server you pick	On a Bluesky or third-party data server
Moderation	Each server sets its own rules	Labelers and block lists you choose, plus Bluesky's own team
Post length	500 characters by default	300 graphemes
Images per post	4	4
Moving accounts	Followers move, posts do not	Same identity across data servers

Who owns Mastodon and Bluesky?

Mastodon's software is developed by a non-profit, and each Mastodon server is run independently by different people or organizations. No single company controls the network. Mastodon's about page describes the project and its non-profit structure.

Bluesky is built by Bluesky PBLLC, a for-profit company, according to the EFF. The AT Protocol is open, and the EFF called Bluesky mostly centralized when it compared the two in 2024. Expect company decisions to matter more on Bluesky than on Mastodon.

How moderation differs

On Mastodon, moderation depends on the server you join. Administrators write the rules, and servers that tolerate abuse get cut off by others through defederation, as the EFF explains. Read a server's rules before you sign up, because experience varies a lot.

Bluesky uses labelers and block lists that you can subscribe to. Problem accounts become less visible rather than disappearing from the network, according to the EFF. Bluesky's own team also acts: its 2025 transparency report says it removed 2,446,334 accounts and pieces of content that year.

Discovery and feeds

Mastodon has no algorithm choosing for you. It's FOSS describes the feed of people you follow as chronological, and the experience as varying by server. Finding people mostly means hashtags, your server's local timeline and following across servers.

Bluesky lets you pick among feeds, including custom ones other people build. A new account usually feels busier on Bluesky, since everyone shares one network and one search. On Mastodon, the first week is mostly following hashtags and people.

Post limits and media

Mastodon's default limit is 500 characters, and a server may set a different one. Links count as 23 characters each. You can attach up to 4 images of up to 16 MB, or one video up to 99 MB, or a poll with up to 4 choices. These are in the Mastodon posting guide.

Bluesky's limit is 300 graphemes, which means an emoji or accented letter counts as one. Posts carry up to four images of up to 1,000,000 bytes each. Draft in the Bluesky character counter to see your count, and compare other networks in the character limits guide.

Can you take your followers with you?

On Mastodon you can move to another server. You set an alias on the new account, then use "Moving to a different account" on the old one, and followers whose software supports it switch automatically. Follows, blocks and mutes are exported and imported by hand, and posts do not move, per Mastodon's guide to moving. There is a 30-day wait before you can move again.

Bluesky is designed so your identity stays the same if you change the server that holds your data, which the EFF calls more flexible. Few people use that yet.

How many people use each?

Mastodon's statistics endpoint shows 736,646 monthly active users, 10,241,101 registered accounts and 7,359 servers on 18 October 2026.

Bluesky had 41.41 million accounts at the end of 2025, up from 25.94 million, and CNBC reported 43 million in March 2026. Those are registered accounts, not active users, so they do not compare with Mastodon's monthly active figure. CNBC also cited a former Bluesky engineering lead's count of active daily posters falling from 1.4 million in late 2024 to about 600,000.

Which should you choose?

Choose Mastodon if you care about who runs the network, want a community with its own rules, or follow niches such as open-source software or science. Expect to spend a few minutes choosing a server.

Choose Bluesky if you are leaving X and want the closest feel, want custom feeds, or want to reach people without learning how servers work. An account on each costs nothing, so many people keep both. Weighing Bluesky against Meta's app instead? See Bluesky vs Threads.

Frequently Asked Questions

Can Mastodon and Bluesky users follow each other?

Not directly, because they use different protocols. Bridges such as Bridgy Fed let accounts on one network appear on the other, as the EFF notes, but you opt in and they are separate projects, not part of either app. Most people keep one account on each.

Is Mastodon free?

Yes. Mastodon is free, open-source software, and the project accepts donations. Individual servers set their own terms, and some ask members for support or limit sign-ups. You do not need to pay to join, though a server you like may be closed to new members.

Do I need to pick a server to join Mastodon?

Yes, you sign up on one server, but you can follow people on any other. Choose one whose rules and topic suit you. If you change your mind, you can move to another server and your followers can come with you, though your posts stay behind.

Is Bluesky really decentralized?

Partly. The AT Protocol is open and anyone can run a data server, but the EFF described Bluesky as mostly centralized in 2024, because the main app and much of the infrastructure remain with the company. Mastodon is more decentralized: thousands of independent servers run it.

Is Mastodon losing users?

Mastodon reports about 737,000 monthly active users today, so it is far from gone, and Bluesky's active posting has also fallen from its late 2024 peak, per CNBC. Both are much smaller than Threads or X. Pick the one where the people you want to follow already are.

Sources

1. Electronic Frontier Foundation, What's the Difference Between Mastodon, Bluesky, and Threads?
2. Mastodon, About Mastodon
3. Mastodon, Posting guide
4. Mastodon, Moving or leaving accounts
5. Mastodon, Network statistics
6. Bluesky, Bluesky 2025 transparency report
7. Bluesky, Action intent links
8. CNBC, Bluesky was a Twitter rival, now it looks to Reddit for inspiration