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 341.6 MB. This is a delta (partial) update that requires 8.0 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6b98843c380549d8c18e07acb750ad03b0cb5188.zip.