I would updates 13.5 iOS for this iPhone
i need to update my iPhone
Question marked as
iOS 12.5.5 is the latest iOS security update for iPhone 5S, 6 & 6 Plus, can’t be update to a higher iOS.
Check -> iPhone type & iOS version -> Go to Settings -> General -> About.
If your iPhone is eligible for an update, you can check by reading this Apple article:
iPhone models compatible with iOS 15
iPhone models compatible with iOS 15.4 – Apple Support (UK)
Then go to: Settings -> General -> Software Update.