How do I update my phone to iOS 16

Update your iPhone, iPad, or iPod touch

• If you have an iPhone 5S or 6/6plus, the highest you can update to is 12.5.7

• If you have an iPhone 6S through 7, or SE 1st generation, you can update to 15.8.2

• If you have an iPhone 8 or X, you can update to 16.7.8

• If you have an iPhone SE (2nd generation or later), or XR through 15, you can update to 17.6

Go to Settings > General > Software Update.

This link will show you how to update your iPhone, iPad, or iPod touch using WiFi -

Update your iPhone or iPad - Apple Support

This link will show you how to update using your computer -

Update iOS on iPhone - Apple Support

Use a computer or the Software Update function in Settings. If you encounter a specific issue, describe it in this thread.

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How can I update my iOS

How do I update my iPhone 8

The instructions have already been provided above in this thread.

But, the iPhone 8 cannot run iOS 17 or iOS 18, if that might be what you are asking.