Download iOS 14.3 (18C66) IPSW file for iPhone 6s or iPhone8,1 from here. This iOS version was released by Apple on the 14th of December 2020.
The iPhone 6s is identified with the identifier iPhone8,1. It was introduced at Apple's 'Hey Siri, Give Us a Hint' event on the 9th of September 2015. It was made available to preorder on 12th September 2015 and started shipping on 25th September 2015. It has the model codes N71AP and N71mAP. It uses the firmware identifier iPhone8,1. There are four model numbers, A1633, A1688, A1691, and A1700.
You can restore this firmware file using iTunes since it is the signed version directly from Apple. Use this file to update your iPhone 6s manually or to repair the system.
iPhone8,1 ipsw file
We have below the latest iOS release IPSW file for iPhone 6s aka iPhone8,1. Check below for available signed iPhone 6s signed IPSWfiles. We will keep this updated when a new iOS release is available.
Device info
Identifier: iPhone8,1
Platform: s8000
BoardConfig: n71ap
BDID: 4
CPID: 32768
→ iOS 14.3 (18C66) for iPhone 6s - Released: 14/12/2020 Size: 4.55GB
Release note for this iOS version can be found here