iOS 9.9.15.1 (build 19B6074) is an official Apple over-the-air update for the iPhone 6s, released on 2021-10-25T17:09:41Z. The update package is 3.89 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: f64148a0524bdce17fc5f38ce6d873bd0a9e1cbc.zip.