Local-first
- Industry term
Local-first is a way of designing apps where each device keeps its own working copy of your data, so you can work offline and changes sync to your other devices and collaborators when you reconnect.
The app reads and writes your data on the device first, so it opens and responds without waiting on a network. Syncing runs in the background, often through the company's server. Since no copy is the master, two people editing the same thing offline need rules that merge their changes later.
Where you’ll meet it
You're choosing a notes app for work, and you write most of your notes on a train with patchy signal. One app's website says it is local-first, and your team would share notebooks in it.
What to do
Before you move your notes in, put a test note through the hard cases. Edit it in airplane mode, then change the same line on two offline devices and reconnect both to learn how the app merges them.
Easy to mix up
| Local-first | Cloud app |
|---|---|
| Your copies stay on your devices | Your data goes with the servers unless you exported it |
Check yourself
Your local-first notes app adds an AI button that summarizes a note. You're about to press it on a private note. What does the app being local-first tell you about where that note will go?
Go deeperCopies can agree on a result that loses what someone meant
Researchers at the lab Ink & Switch set out the idea in a 2019 essay, “Local-first software.” Many local-first apps merge edits with CRDTs (conflict-free replicated data types), structures built so every copy reaches the same result whatever order the changes arrive in.
If one person deletes an item while another renames it, every copy settles on the same outcome and one person's edit is lost, with different apps choosing differently which one. Keeping full copies on devices also adds work a server would otherwise handle, such as backups, encryption on each device, and recovery after a device is lost.