iOS 12.1 (build 16B5077c) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2018-10-09T17:05:55Z. The update package is 263.1 MB. This is a delta (partial) update that requires 12.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: d5b76bf4e6285f25dc2d0394c6011250a5bbb694.zip.