iOS 9.2.1 (build 13D15) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2016-01-19T17:59:50Z. The update package is 240.06 MB. This is a delta (partial) update that requires 9.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: bd0304613c68e20a8da13aa4a51a49695f13cdaf.zip.