DIDs, handles, and providers

Every Atmosphere account has three pieces:

• A DID: a permanent ID for you. Never changes.
• A handle: a human-readable name. Can change anytime.
• A provider (also called a PDS): the server that stores your data.

The three pieces work together. You don't usually think about them directly because apps like Sifa hide them. Knowing what each does makes the rest of the network easier to follow.

DID: your permanent ID

A DID is a long string that looks like:

did:plc:abcdef1234567890

It's your account's true name. The handle you use day to day is a friendly alias on top. The DID is what Sifa stores when it writes records about you, what other Atmosphere apps refer to you by, and what stays the same when you move providers, change your handle, or repoint your custom domain.

You rarely see your DID unless you ask for it. Sifa shows it in profile settings and on the developer-facing parts of the AT Protocol. You don't memorise it. You copy-paste it if something needs it.

The DID never changes. The whole point of the Atmosphere is that your identity is portable, and the DID is what makes that work.

Handle: your friendly name

A handle is what people actually call you. Two common shapes:

• Provider subdomain: alice.bsky.social (handle issued by Bluesky), alice.eurosky.social (handle issued by Eurosky).
• Your own domain: alice.com, alice.example.org. Set up by adding a DNS record or a /.well-known/atproto-did file on your own site.

Handles can change. If you stop liking alice.bsky.social, switch to alice.com tomorrow. Your DID stays the same, your followers stay the same, your Sifa profile stays the same. People who linked to your old handle get redirected.

Want your own domain as your handle? See Use your own domain as your handle.

Provider: where your account data lives

A provider is the company or organisation running the server that stores your records. In AT Protocol jargon the server is called a PDS (Personal Data Server); the company running it is the provider.

Some current ones:

• Bluesky (bsky.social): the original, US-hosted.
• Eurosky (eurosky.social): EU-hosted, GDPR-aware.
• Tangled (tangled.org): EU-hosted, run for developers.
• Blacksky (blacksky.community): community-run.
• …and others.

Sifa is not a provider. Sifa is an app that reads from and writes to your provider on your behalf. Your career history, posts, and profile records live on your provider, not in Sifa's database.

You can change providers without losing anything. Migrate from Bluesky to Eurosky and your followers, posts, profile data, and Sifa records come with you. The DID stays the same. The handle may need re-pointing if you used a provider subdomain.

How they fit together: a worked example

Say you create a Bluesky account today. Behind the scenes:

1. Bluesky's PDS assigns you a DID like did:plc:abc123. Permanent.
2. You pick a handle: alice.bsky.social. Friendly, changeable.
3. Your records (posts, follows, profile) live on Bluesky's PDS.

You sign in to Sifa with alice.bsky.social. Sifa looks up your DID, reads your existing records from Bluesky's PDS, and creates new Sifa-specific records (positions, education, skills) on Bluesky's PDS.

A year later you decide you want your data on EU infrastructure. You migrate to Eurosky:

1. Eurosky becomes your new provider.
2. Your DID (did:plc:abc123) doesn't change.
3. Your handle becomes alice.eurosky.social (or you point your own alice.com at the new provider).
4. All your records, including Sifa records, move with you.

Sifa works the same as before. No re-import, no re-create. That's the point.

Want to go deeper

• Your data on a provider: what records look like, where they live, how to inspect them.
• Apps, AppViews, and the firehose: how Sifa reads your records and shows them on your profile.
• What is the Atmosphere?: the bigger picture.