How do I update my iPhone 6s Plus to latest iOS version?

Your iPhone 6s Plus is almost over 10 years old and is long beyond support for the latest iOS updates. The furthest it can go is iOS 15.8.4. It will never run the latest iOS version, which currently is iOS 18, due to lack of hardware and RAM. You'll need to purchase a newer iPhone for that.

There was a recent update for your iPhone 6s. The most up to date version for your phone is now iOS 15.8.4

You can check to see if you already have this version by tapping Settings > General > Software Update.

The iPhone 6s cannot run iOS 16, 17 or 18......if that might be what you are asking about.

An iPhone 6s, iPhone 6s Plus, iPhone 7, iPhone 7 Plus, or iPhone SE 1 isn't capable of 16 or above; they require an A11 or better CPU. To install 15.8.4, use a computer or the Software Update function in Settings.

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