Sync & storage infrastructure

The data layer for local-first apps.

Halden keeps data in sync across devices and stores it durably — one engine, a clean API, no moving parts to manage.

Read the documentation →$ halden serve
Halden Sync·Realtime sync·Durable storage·REST & streaming API·Single binary

Capabilities

Realtime sync

Changes replicate across every connected client in milliseconds, with deterministic conflict resolution.

Durable storage

An append-only log with point-in-time recovery keeps every write safe and auditable.

One clean API

A single REST and streaming interface — no SDK lock-in, no schema migrations to babysit.

Running in three steps.

Point Halden at a directory and connect. That's the whole setup.

  1. 1Start the engine on any host.
  2. 2Open a namespace for your app.
  3. 3Read and write through the API — sync is automatic.
# start the engine $ halden serve --data ./store # create a namespace $ halden ns create notes → namespace ready · api · sync # write through the API $ curl -X PUT /v1/notes/today \ -d '{"body":"hello"}'