iOS 8.3 (build 12F70) is an official Apple over-the-air update for the iPhone 5s (GSM), released on 2015-04-08T17:56:15Z. The update package is 280.61 MB. This is a delta (partial) update that requires 8.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6daac528678922d8610cda9c4d66d18b4be533d0.zip.