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 139.76 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: 87bb007e3a07d925c89dba550df21f22f06f7b5e.zip.