iOS 9.1 (build 13B5119e) is an official Apple over-the-air update for the iPhone 4s, released on 2015-09-23T17:55:08Z. The update package is 1.1 GB. This is a delta (partial) update that requires null already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: b35e8032c5850700f909fef9a7fa2a95db5c8157.zip.