iPadOS 9.2.1 (build 13D15) is an official Apple over-the-air update for the iPad 4 (WiFi), released on 2016-01-19T17:59:13Z. The update package is 991.52 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: 48b3f1606abb2803534b646b6bf21f1fdf9bfc95.zip.