iOS 8.4 (build 12H143) is an official Apple over-the-air update for the iPhone 4s, released on 2015-06-30T15:51:17Z. The update package is 824.26 MB. This is a delta (partial) update that requires 7.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6064407407566c851aa42149127dce3401a337f1.zip.