iOS 8.4 (build 12H4086d) is an official Apple over-the-air update for the iPhone 4s, released on 2015-04-27T17:47:05Z. The update package is 118.8 MB. This is a delta (partial) update that requires 8.4 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: e00900c0f5776c62a7640e6fed1879974fcf98f9.zip.