iOS 9.1 (build 13B5143) is an official Apple over-the-air update for the iPhone 4s, released on 2015-10-21T17:15:46Z. The update package is 1.09 GB. This is a full OTA update that can be applied from any compatible base version. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: f27cc7d37e1e4051bea2a440e02caa2a5a795063.zip.