# Offline & reconnection (/docs/guides/offline)



The engine listens to the browser's `online` and `offline` events (once mounted, the
React hooks do this for you).

When the browser goes offline:

* No new uploads start; queued items wait.
* Uploads that fail with a network error are **paused** with `pauseReason: "offline"`
  instead of failing, and the attempt doesn't count against the retry budget.
* `UploadStatus` shows “Waiting for network”.

When it comes back online, offline-paused items are re-queued automatically. Resumable
adapters continue from their last part; others restart.

```ts
uploader.on("online", ({ online }) => console.log(online ? "back online" : "offline"))
const online = useNetworkStatus()
```

<Callout title="What “online” means">
  `navigator.onLine` only says a network interface is up, not that your server is
  reachable. That's why every network failure is also retried with exponential backoff,
  online or not.
</Callout>

## Testing it [#testing-it]

In Chrome DevTools, set **Network → Offline** during an upload. With a resumable adapter
(try the [pause/resume example](/examples#pause-resume)), go back online and watch it continue.