What kind of account is this?
One account.
The whole atmosphere.
branchline doesn’t have its own sign-up. It uses an Atmosphere Account — the same account that powers Bluesky and a growing number of other apps built on the AT Protocol. One login, yours to keep, wherever you go.
The short version
Think of an Atmosphere Account as a passport. It’s an identity that belongs to you, not to any single app, and it comes with a handle (your name, like alice.bsky.social) and a small corner of the web where your writing actually lives. When you sign in to branchline, your account’s host asks whether you’d like to let branchline read and write on your behalf. Say yes, and you’re in.
The same account works in Bluesky, in other reading and writing apps, in feed builders, in image hosts — anything built on the protocol. If branchline disappears tomorrow, your words don’t. They live with you.
Why it’s set up this way
On most platforms, your account belongs to the platform. If they go away, change the rules, or decide they’d rather not host you, your writing goes with them. The atmosphere inverts that: your identity and your writing live in your account, and apps like branchline are just windows onto it. No single company decides what you can take with you when you leave.
Where to get one
There are three common paths, from easiest to most involved.
Sign up through an app. Some apps double as account hosts — when you make an account there, you’re also making an Atmosphere Account that works everywhere else. The most popular today is Bluesky. Free, takes a minute, and the handle you pick there works here without any extra setup.
Use an independent provider. A small but growing number of hosts exist only to hold Atmosphere Accounts — they’re not apps themselves. Some are community-run, some lean on privacy, some are built around a particular domain you’d like to use for your handle. If you’d rather your account not live on Bluesky’s infrastructure, this is the route.
Run your own. If you’re technical and want full control, you can run the host software yourself on your own server. The protocol is open; anyone can be a provider. Your handle can be (and probably should be) a domain you already own.
Whichever path you pick, the account works the same way in branchline. The sign-in flow is always: type your handle, approve the consent screen on your host, come back here. branchline never sees your password — it only ever talks to your host through the tokens you grant it.
What branchline can and can’t do with it
When you sign in, your host shows you a consent screen listing exactly which collections branchline is asking for. We only ever ask for the ones we need to publish your buds and pollen, and (optionally) to crosspost to Bluesky. We can’t read your DMs, your follows, or anything else — the protocol won’t let us, and we never asked. The full breakdown lives on the policy page.
Ready?
Once you have a handle, head back to the sign-in page and type it in.
More on the atmosphere itself
If you want the bigger picture — what the atmosphere is, which apps already exist in it, why anyone’s building this — a good canonical explainer lives at atmosphereaccount.com. We won’t try to outdo it here.