iOS 10.3 (build 14E277) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2017-03-27T16:57:54Z. The update package is 572.44 MB. This is a delta (partial) update that requires 10.2.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: bf32506c01f58a835d9ab3397336e92920962a6a.zip.