iOS 8.3 (build 12F70) is an official Apple over-the-air update for the iPhone 5 (GSM), released on 2015-04-08T17:56:10Z. The update package is 391.44 MB. This is a delta (partial) update that requires 8.0.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 01fe1996500435a9a6f633cde97a4d5b6f571767.zip.