> ## Documentation Index
> Fetch the complete documentation index at: https://docs.zerokeyusb.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Web Time Sync Tool

> Use the browser-based helper to send accurate Unix time to ZeroKeyUSB.

The ZeroKeyUSB firmware repository includes a lightweight web application that runs locally in your browser. It connects to the device over WebUSB and pushes the current epoch so TOTP codes stay in sync.

***

## Requirements

* Chromium-based browser (Chrome, Edge, Brave) with WebUSB enabled
* ZeroKeyUSB unlocked and connected via USB-C
* Local copy of the **`tools/web-time-sync`** directory served via `npm run dev`

No Internet access is necessary once the page is loaded.

***

## Launching the tool

```bash theme={null}
cd tools/web-time-sync
npm install
npm run dev
```

Open the printed local URL (typically `http://localhost:5173`) in your browser. You should see the ZeroKeyUSB logo and a “Connect” button.

***

## Sending the time

1. Click **Connect** and select your ZeroKeyUSB from the device list (`ZeroKeyUSB CDC`).
2. The page displays the current Unix epoch and a countdown to the next 30-second boundary.
3. Press **Sync now** when the device requests time (shows `REQTIME`).
4. The tool sends `SETTIME <epoch>` automatically and confirms success with a toast notification.

If the device was already in sync, it responds with `OK` and no changes are made.

***

## Safety features

* The tool only communicates with USB devices whose vendor/product IDs match ZeroKeyUSB.
* All commands are visible in the on-screen console for auditability.
* No data leaves the browser tab; telemetry and analytics are disabled.

<Alert>
  Close the tab when finished. Leaving WebUSB connections open can prevent other applications from accessing the serial port.
</Alert>

***

## Troubleshooting

| Issue                     | Resolution                                                                      |
| ------------------------- | ------------------------------------------------------------------------------- |
| Browser cannot access USB | Make sure you are using a Chromium browser and have granted device permissions. |
| `Failed to send epoch`    | The device might be locked; unlock it and try again.                            |
| Tool closes unexpectedly  | Check the terminal running `npm run dev` for errors and restart the dev server. |

The web time sync tool offers a user-friendly way to keep your hardware authenticator aligned without installing heavyweight software.