You cannot downgrade from a newer version (like iOS 16) to 12.1. 📥 How to Download (Archive Only)
If you need the file for archival or advanced research purposes, you can find it on community-driven sites: Go to the iPhone 8 (GSM) page on IPSW.me . Identifier: Ensure you choose iPhone10,4 (the GSM model). Build Number: The specific build for iOS 12.1 is 16B92 . 🛠️ Official Installation Method (Latest Available)
iTunes or Finder will block the installation of unsigned firmware.
If you have a signed IPSW file and want to install it manually: iPhone 8 (GSM) IPSW Download - iClarified
from third-party archives, but you under normal circumstances . Apple stopped "signing" iOS 12.1 for the Go to product viewer dialog for this item. in December 2018. ⚠️ The Signing Problem
You can technically download the iOS 12.1 IPSW file for your iPhone 8 (GSM) Go to product viewer dialog for this item.