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 303.85 MB. This is a delta (partial) update that requires 8.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b8f0cc8883aad07c686c201710ef9ed75d724a79.zip.