iOS 8.3 (build 12F70) is an official Apple over-the-air update for the iPhone 4s, released on 2015-04-08T17:56:09Z. The update package is 819.14 MB. This is a delta (partial) update that requires 7.1.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 76cad39b62417568e8d05107ff4e1a3236cad98d.zip.