iOS 9.0 (build 13A344) is an official Apple over-the-air update for the iPhone 4s, released on 2015-09-16T18:02:13Z. The update package is 809.17 MB. This is a delta (partial) update that requires 8.4.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 434d7b328710bcae62453d3ff514efcd011f38be.zip.