iOS 9.1 (build 13B143) is an official Apple over-the-air update for the iPhone 4s, released on 2015-10-21T17:16:00Z. The update package is 19.74 MB. This is a delta (partial) update that requires 9.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 17ca2e4f8dbb6336057b59786629253082f5e5a1.zip.