iPadOS 9.1 (build 13B5130b) is an official Apple over-the-air update for the iPad 4 (GSM), released on 2015-09-30T17:58:06Z. The update package is 175.52 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: f4641a6039edc1aed83f15c5d3f3bad08d904762.zip.