iPadOS 9.1 (build 13B143) is an official Apple over-the-air update for the iPad 4 (WiFi), released on 2015-10-21T17:15:52Z. The update package is 988.94 MB. This is a delta (partial) update that requires 8.1 already installed. This update is no longer signed by Apple, meaning it can no longer be applied on-device through Settings.

Payload file: 0897871822478b30850ec62b66e0b6bb62614f28.zip.