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Multiple Devices

SuperFast supports any number of devices connected to a single store account. Each device has its own local SQLite database and syncs independently with the server.

How Multi-Device Works​

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All devices share the same store data. Changes made on any device propagate to all others via push/pull sync.

Adding a Second Device​

If You Have the Store Credentials​

  1. Install SuperFast on the new device (Installation Guide).
  2. On first launch, tap Log In to Existing Store.
  3. Enter:
    • Store ID — found in Settings → General on any connected device
    • PIN — the 4-digit store PIN
    • Server URL — same URL used on the first device
  4. Tap Login.

The device registers with the server, receives a device-specific JWT, and downloads the full dataset from the server. This initial sync may take 5–30 seconds depending on data volume.

If You Don't Have the Credentials​

Ask any existing device owner to:

  1. Open Settings → General.
  2. Share the Store ID.
  3. Share the PIN (verbally — do not send the PIN over an insecure channel).

Device IDs​

Each device is automatically assigned a unique deviceId (UUID) when it first registers with the server. The device ID is:

  • Stored locally in %APPDATA%\superfast\device.json (Windows) or in the app's private storage (Android)
  • Sent with every API request as the X-Device-ID header
  • Used by the server to track which changes came from which device (to avoid sending a device its own changes during pull)

Viewing Connected Devices​

From any device:

  1. Open Settings → Server Dashboard tab.
  2. The Connected Devices section lists all registered devices with:
    • Device ID (first 8 characters)
    • Device Name
    • Last Seen timestamp
    • Status (Active / Inactive)

Removing a Device​

To disconnect a specific device from the store:

From the Device Itself​

  1. Open Settings → Cloud Sync.
  2. Tap Disconnect.

From Another Device (Remote)​

If the device is lost or you can't access it:

  1. Open Settings → Server Dashboard.
  2. Find the device in the Connected Devices list.
  3. Tap Logout Device (danger zone).
  4. The device's JWT is revoked server-side. It can no longer push or pull until it re-authenticates.

Sync Behavior with Multiple Devices​

Typical Flow​

09:00  Device A creates customer "Khalid"      → pushed to server
09:01  Device B pulls → receives customer "Khalid"
09:05  Device B records debt for Khalid        → pushed to server
09:06  Device A pulls → receives the debt transaction

Simultaneous Offline Use​

(Network is down)
10:00  Device A records Khalid debt  → sync_queue (pending)
10:02  Device B records Khalid payment → sync_queue (pending)

(Network restored at 10:30)
10:30  Device A pushes → server stores debt (ts=10:30:01)
10:30  Device B pushes → server stores payment (ts=10:30:02)

Both transactions are preserved (different UUIDs, no conflict)

10:31  Device A pulls → gets Device B's payment
10:31  Device B pulls → gets Device A's debt

Result: Both devices now have both transactions.

Best Practices​

Designate Roles​

Consider designating devices to specific roles:

  • Counter device — records all transactions throughout the day
  • Manager device — reviews reports, manages customers, approves credit

WhatsApp Device​

WhatsApp linking is per-device. Designate one device as the WhatsApp device to avoid confusion. Other devices can still trigger WhatsApp sends — the server routes all WhatsApp calls through the connected instance.

Keep One Device Online​

For reminders with WhatsApp auto-send, at least one device should remain online and running SuperFast. A dedicated Android phone or a desktop PC works well as the "always-on" device.

Sync Before Handing Off​

Before switching from one device to another for critical entry, tap Sync Now on both devices to ensure they are fully up to date.

Device Limits​

There is no hard device limit per store in the software. Practical limits depend on:

  • Server capacity (RAM, DB connections)
  • Network bandwidth

For most small stores, 2–5 devices is typical. The server configuration allows up to 100 concurrent connections by default.

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