iOS 8.3 (build 12F70) is an official Apple over-the-air update for the iPhone 4s, released on 2015-04-08T17:56:10Z. The update package is 296.54 MB. This is a delta (partial) update that requires 8.1.3 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 697ac59e071c01c4c2ee2de07ff7f64e8c12d5dc.zip.