Apple's updated operating system for iPhone and iPad - iOS 11 - is out now, with regular updates continuing to roll out.
Not all updates are compatible with older devices, however. Apple acknowledges the reality that hardware gets slower as it ages, and software gets more and more demanding for devices to run: so a phone that was state-of-the-art five years ago is unlikely to be able to run the latest software now.
Indeed, in the past we have sometimes found that borderline cases - devices that only just sneak into the list - are able to install the new OS but struggle to run it well, and run a bit slower than with the previous version of iOS.
This year the axe has fallen on the iPad 4, the iPhone 5 and the iPhone 5c. These devices will not be permitted to install iOS 11.
Here's a list of every Apple device that supports iOS 11:
- iPad Air 1, iPad Air 2, iPad Pro (12.9, 2015), iPad Pro (9.7), iPad 2017, iPad Pro (10.5), iPad Pro (12.9, 2017), iPad 2018
- iPad mini 2, iPad mini 3, iPad mini 4
- iPhone 5s, iPhone 6, iPhone 6 Plus, iPhone 6s, iPhone 6s Plus, iPhone SE, iPhone 7, iPhone 7 Plus, iPhone 8, iPhone 8 Plus, iPhone X
- iPod touch (sixth generation)
So if you've got an iPad Air 1 or later, an iPad mini 2 or later, an iPhone 5s or later, or a sixth-generation iPod touch, you can get iOS 11 now.