You probably got to this post because you Googled some question about what exactly “the fediverse” is, what “ActivityPub” actually means, or what would happen if you turned on federation on your Threads account today. I’m not going to get into the technical weeds or make this a comprehensive explainer, I just want to get you what you need to grasp the basic concept of federation and then move on with your day.

Also there are more services than Threads and Mastodon built on ActivityPub, but for the sake of clarity, I’m not going to mention them in this post. We’re just focused on nailing the concept here, specifically from the perspective of a Threads user who wants to know if they should turn it on.

It’s like email

"It's like email" is is the best 3 word explanation I’ve got and I think it’s a pretty good one. If you wanted to have a way to send and receive emails, you need to get an email account. That account can be through Gmail, Outlook, or a bunch of other providers, and you can choose the one that you like most. What other people use isn’t a huge deal because email services all work together. I use Gmail, but if you choose Outlook, it doesn’t matter at all to me, I just need to know your username: something like [email protected].

This is possible because “email” is the protocol and Gmail and Outlook are services built on this protocol. They compete on features and user interfaces, but at the end of the day they all work together.

Now let’s move the conversation over to Threads and Mastodon.

The explainer is basically exactly the same as the above email example, just swap in Threads and Mastodon for Gmail and Outlook and ActivityPub for email.

If you want to create a social media account in 2024, you can choose from an assortment of ActivityPub providers like Threads, Mastodon, or others. I have a Mastodon account, but you can choose to create an account on Threads or Mastodon, it doesn’t really matter, I just need to know your username: something like @[email protected].

This is possible because “ActivityPub” is the protocol and Threads and Mastodon are services built on this protocol. They compete on features and user interfaces, but at the end of the day they all work together.

Why this sounds weird

Email is a really close comparison, but it’s far from the only one. The web also comes to mind, as you can use Chrome and I can use Safari and someone else can use Firefox and we can all see the same sites through whatever browser we prefer. RSS is a little more niche, but it’s another good example of a technology that lets you follow things like this blog through a bunch of different apps. Did you ever wonder why podcasters can say, “subscribe in your favorite podcast app”? Podcasts are built on RSS, and RSS fundamentally allows this freedom; it’s great!

But over the past 20 years social networks like Facebook, Instagram, Twitter, and TikTok have made closed social media the norm, and it’s been so long since we’ve had options that are more open to user choice that it can almost feel weird and complicated, even though we use things like email every single day without thinking twice about it.

Common misconceptions I see on Threads

After seeing Meta enable “federation” (aka allowing your Threads account to talk to ActivityPub) on Threads recently, my feed has been full of people figuring out what it means if they flip the switch. I’ve seen some people say some very wrong things with a lot of confidence, so I thought I’d tackle a few of the more common misconceptions and questions I’ve seen here.

What do I need to do on Mastodon after I enable federation on Threads?

Literally nothing. As soon as you turn on federation for your Threads account, all posts from that point on (and nothing from before you turned it on) will be available for Mastodon users to like, boost (retweet), and they can follow your account.

Do I need to link a Mastodon account to my Threads account?

This is something I see a lot, but no, you do not need to ever use Mastodon yourself. This isn’t cross-posting, it’s literally just letting people from other apps follow your literal Threads account.

Think about the email example above: when you send an email from Gmail to an Outlook address, you don’t need to have an Outlook account set up to forward the message to your friend, it just sends directly.

Mastodon’s sign up is so confusing I don’t know what to do. I’m just not going to bother with it.

I know I’m drilling this in a lot, but you literally do not need to have a Mastodon account. By not turning on federation from Threads, all you’re doing is making it so people who did figure out how to sign up for Mastodon and like it to not be able to follow you. You can choose to do that, but you never have to touch Mastodon if you don’t want to.

They put my Threads posts on Facebook and Instagram and I don’t want that.

Yes, this was sucky, although it’s a completely separate thing from federation. Facebook and Instagram aren’t using ActivityPub in any way, so federating your Threads account doesn’t put your Threads posts on Meta’s other apps.

If you want to make sure your Threads stuff doesn’t show in Facebook or Instagram, go to your Threads Privacy settings page and make sure those are turned off.

This is one of the reasons that federation and making your posts available to Mastodon users is opt-in. I personally think the more people doing this the better, but it isn’t right to start putting things you thought were only on Threads elsewhere without your permission, so making this opt-in is a mercifully user-friendly move by Meta.

The asterisks

Updated as of June 25, 2024

The biggest asterisk on this comparison right now is that Meta has only rolled out limited ActivityPub support as of this writing. As it stands today, turning on federation from Threads will make it so Mastodon users can follow your Threads account and you’ll get notifications in Threads when people like and boost your posts. You'll also see replies from Mastodon users and you can like those replies.

But you can’t follow Mastodon users back, you can’t reply to Mastodon posts, and you can’t do the biggest thing that’s awesome about ActivityPub: migrate your whole account from one service to another without losing any followers.

Meta has said that these features are all coming in time and that federation is a beta right now. I will try to remember to update this post as those things are added.