Symptoms

  • After “Preparing update”, iOS shows “Unable to Verify Update” or “An error occurred installing iOS.”
  • The install button does nothing, or the phone reboots back to the same prompt.
  • Storage is nearly full.

What causes “Unable to Verify Update” (iOS)

  • Wi-Fi dropped during the verification step (verification needs an active connection).
  • Not enough free storage to expand and install the update.
  • The downloaded update file is corrupt or half-downloaded.

How to fix it

  1. Confirm a strong Wi-Fi connection and at least a few GB free (Settings → General → iPhone Storage).
  2. Delete the downloaded update: Settings → General → iPhone Storage → find the iOS update → Delete Update. Then re-download it in Settings → General → Software Update.
  3. Restart the iPhone and try again; if it still fails, update via a computer (Finder on macOS, Apple Devices app on Windows).
How to confirm the fix: The update verifies, installs, and the device boots into the new iOS version.

Prevent it from coming back

Keep 5–10 GB free, update on stable Wi-Fi, and keep the phone on power during the update.