What Is Local-First Software?

The term describes where the authoritative copy of your data sits. In a cloud application, the real document lives on the provider's server and your screen shows a view of it. In a local-first application, the real document lives on your computer, and anything else, such as a backup or a copy on another device, is derived from it.

Local-first is a design principle rather than a product category. A word processor, a point of sale system, a project planner or an email client can each be built local-first or cloud-first. The question is always the same: if the vendor's servers disappeared tomorrow, could you still open, edit and keep your work?

The application reads and writes to storage on the device: files in a folder, or a database file the application manages. Every action completes locally, so the application does not wait for a round trip to a server before saving a change.

Where more than one device or person needs the same data, a local-first design adds synchronisation on top. Each device keeps a complete copy and exchanges changes with the others when a connection is available. Changes made while apart are merged later. The connection makes collaboration possible; it is not required for the work itself.

• Data is stored on the device first, in a format the user can back up.
• The application is fully usable with no connection.
• Synchronisation, where it exists, is optional and happens in the background.
• The user can keep and move their data without the vendor's involvement.

Speed is the most noticeable one. Opening a file, searching or saving a change happens at the speed of the disk rather than the speed of the network, so the application feels immediate.

Reliability follows. Work continues through an outage, on a train, in a basement shop or on a site with no signal. Nothing is lost because a connection dropped during a save.

Control is the third. The data is on hardware you own, which makes backup, retention and privacy decisions yours. It also means your access does not end if an account lapses or a service is withdrawn.

Local-first moves responsibility as well as control. If the only copy of your data is on one laptop and that laptop fails, the data is gone unless you backed it up. A good local-first application makes backups easy, but someone still has to take them.

Real-time collaboration is harder to build without a central server, so some local-first tools offer file sharing or later synchronisation instead of many people typing in one document at once. Access from a borrowed computer through a web browser is also usually not possible, because the application and the data are on your own machine.

A spreadsheet saved as a file on your disk is the oldest example of local-first working. Modern examples include note-taking tools that store notes as files in a folder, retail systems where each till holds a full copy of the business and merges sales later, and form tools that collect responses as files that can travel by USB drive.

It suits work where the connection cannot be trusted, where the data is sensitive, or where the cost of losing access is high: a shop till, client files, financial records, creative projects with large media. It also suits anyone who wants to own their tools rather than rent access to them.

It is a weaker fit when the main value of the software is live collaboration among many people in different places, or when people need to reach the same data from any device through a browser. In those cases a cloud tool, or a hybrid with local copies, may serve better.

Local-first overlaps with, but is not the same as, offline-first; the difference is explained in what offline-first software means. For a side by side view, read local-first versus cloud software. The local-first software hub collects applications built this way.

Aevornix applications are built on this principle. Aevornix Workspace keeps pages, records and tasks in a workspace folder you own. Aevornix POS runs a shop from a business file on its own computer, with each till keeping a full copy. The Aevornix Suite applications, such as Aev Word, keep documents as files on your computer with no account or server.