What is local-first software? Your data on your device first

Where the main copy lives

Most apps you use today are cloud-first. The real copy of your notes, photos or files sits on the company’s server. Your phone shows a view of it, and often can’t do much without a connection.

Local-first turns that around. The phrase comes from an essay by four researchers at the lab Ink & Switch. In their words, the app keeps the primary copy of your data on your device, and servers hold secondary copies that help you reach it from more than one device.

That one change has a long list of effects.

What you get

The essay lists seven ideals. In plain terms:

1. No waiting. Opening something doesn’t wait on a round trip to a server.
2. Not stuck on one device. Sync and backup still exist; they just aren’t the main copy.
3. The network is optional. On a plane, in a basement, abroad without data, the app still works.
4. Working together where the app supports it.
5. It lasts. If the company shuts down, the data on your device is still yours and still opens.
6. Private by default, because a server that holds only a helper copy can hold it in encrypted form.
7. You keep control, including the choice to leave.

All seven come from the same essay. Not every app meets all of them, and a few are hard to build.

What it costs you

Local-first moves some duties from the company to you.

• Backups are your job. If the only copy is on your phone and the phone breaks, the data goes with it. Turn on whatever backup the app offers.
• Keys are your job. When the server holds only encrypted data, nobody there can reset your access. That is why such apps hand you a recovery key and ask you to keep it.
• Sharing is harder. Sending a link to a file on a server is simple. Sending something that lives on your phone takes an extra step.

These are real costs. They are also the same thing as the benefits, seen from the other side.

How to tell if an app is local-first

Ask these questions before you trust an app with years of data.

1. Does it work in airplane mode? Open it with no network. If it shows a spinner or an error, the main copy is on a server.
2. Does it need an account? An account is not proof of cloud-first, but an app with no account has nowhere else to keep your data. The guide to vaults with no account goes deeper.
3. What does the backup hold? Readable files, or encrypted ones only you can open? See zero-knowledge encryption.
4. Can you get your data out without the app? A local-first app should leave you something to take with you.

When cloud-first is the better fit

Local-first is not always right. If you edit the same document with ten people at once, or you want any device in the world to show your files after one sign-in, a cloud-first service does that with less effort. Pick by what matters most to you for this kind of data.

Where Sealed helps, and where it doesn’t

It helps because your files stay on your phone unless you choose otherwise. Your files never leave your iPhone unless you turn on iCloud backup or export them yourself. Sealed has no account, so there is nothing to sign up for.

It helps when you add a backup, which holds only encrypted data. Backup goes to your own iCloud account, not to a server of ours. Files, names, notes and record fields are encrypted on your iPhone before they are uploaded, so iCloud receives only ciphertext.

It helps with a copy that opens without the app at all. The open copy keeps a copy of your vault in your iCloud Drive, in a folder named Sealed, that opens without the app on any computer, with your recovery key and the Sealed reader. The open copy page explains it.

It doesn’t keep a copy for you. If you lose the phone and never turned on a backup, nothing brings the vault back. Because your key never reaches us, we cannot recover your vault or reset your passcode for you.