iOS 9.1 (build 13B143) is an official Apple over-the-air update for the iPhone 4s, released on 2015-10-21T17:15:59Z. The update package is 850.37 MB. This is a delta (partial) update that requires 8.2 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 6204e93d3b52e83abfa63225224f072ccd1ac131.zip.