kernel/system

Device identity, live network state, and battery — three hooks, no config required.


import { useDeviceInfo, useNetwork, useBattery } from 'react-native-kernel/system';

`useDeviceInfo()`


import { useDeviceInfo } from 'react-native-kernel/system';
 
function DeviceCard() {
  const device = useDeviceInfo();
 
  return (
    <Text>
      {device.brand} {device.model} — {device.systemName} {device.systemVersion}
    </Text>
  );
}

Return value

Field	Type	Notes
`brand`	`string`	`"Apple"` on iOS, `Build.BRAND` on Android
`model`	`string`	Hardware identifier (e.g. `iPhone16,1`) / `Build.MODEL`
`systemName`	`string`	`"iOS"` / `"Android"`
`systemVersion`	`string`	OS version string
`isEmulator`	`boolean`	Simulator / emulator detection
`screenWidth` / `screenHeight`	`number`	From `useWindowDimensions()`, so these re-render on rotation
`vendorId`	`string`	See identifiers below
`installationId`	`string`	See identifiers below
`macAddress`	`string`	Always `"02:00:00:00:00:00"` — see note below

Device identifiers

There are three different “identify this device” fields, each with a different lifetime — pick the one that matches what you actually need:

Field	Resets when	Requires
`vendorId`	All apps from the same vendor (iOS) / factory reset or app re-signing (Android) are removed	Nothing
`installationId`	This app is uninstalled, or its local storage is cleared	Nothing (generated + persisted by `react-native-kernel/storage`’s fast KV store on first read)
`macAddress`	Never changes, because it’s a constant	N/A

vendorId — iOS: UIDevice.identifierForVendor. Android: Settings.Secure.ANDROID_ID. No permission needed on either platform.
installationId — a UUID this package generates itself on first access and persists via kernel/storage’s synchronous KV store. Stable across restarts and OS updates.

macAddress is not a usable identifier. Both iOS (since iOS 7) and Android (since Android 6 / API 23) hardcode this to "02:00:00:00:00:00" for every third-party app — there is no public API that returns the real hardware MAC address anymore. The field is included for completeness only. Use vendorId or installationId instead.

`useNetwork()`


import { useNetwork } from 'react-native-kernel/system';
 
function ConnectivityBanner() {
  const network = useNetwork();
 
  if (!network.isConnected) {
    return <Banner>You're offline</Banner>;
  }
  return <Text>Connected via {network.type}</Text>;
}

The hook re-renders whenever connectivity changes (WiFi ↔ cellular, connect/disconnect, etc.) — you don’t need to subscribe to anything yourself.

Return value

Field	Type	Notes
`isConnected`	`boolean`
`isInternetReachable`	`boolean`	Not just “has a network” — validated internet access
`type`	`string`	One of `'wifi'`, `'cellular'`, `'ethernet'`, `'none'`, `'unknown'`
`ipAddress`	`string`	Local IP on the active interface, `""` if unavailable
`isWifiEnabled`	`boolean`	See platform note below
`ssid`	`string`	`""` unless the required permission/entitlement is granted — see Installation
`bssid`	`string`	Same requirements as `ssid`
`carrier`	`string`	`""` when unavailable; see note below

isWifiEnabled means different things per platform. Android reads the real WiFi radio power state (WifiManager.isWifiEnabled). iOS has no public API for radio state at all, so this field falls back to “is the current connection over WiFi” instead — it is not a radio-power check on iOS.

ssid/bssid resolve asynchronously on iOS. Because the only current, non-deprecated API for this (NEHotspotNetwork.fetchCurrentWithCompletionHandler:) is callback-based, the value starts as "" and fills in via a follow-up update shortly after a connection is made — the hook re-renders when it resolves, same as any other network change. Android resolves these synchronously.

carrier is best-effort. No special permission is required on either platform, but Apple deprecated CoreTelephony’s carrier APIs in iOS 16 with no replacement, so recent iOS versions may return a generic placeholder rather than the real carrier name. This field is genuinely empty (not a bug) on devices/simulators with no cellular hardware.

`useBattery()`


import { useBattery } from 'react-native-kernel/system';
 
function BatteryPill() {
  const battery = useBattery();
  const label = battery.level < 0 ? 'unknown' : `${Math.round(battery.level * 100)}%`;
  return <Text>{label}{battery.isCharging ? ' ⚡' : ''}</Text>;
}

Return value

Field	Type	Notes
`level`	`number`	`0`–`1`, or `-1` when the platform can’t report it (e.g. iOS Simulator)
`isCharging`	`boolean`
`isLowPowerMode`	`boolean`	Low Power Mode (iOS) / Battery Saver (Android)

Next: kernel/network.