Apple released iOS 11.4 for iPads and iPhones yesterday, and it includes a new feature that makes it easier to keep iMessages in sync between your iPhone and iPad.
The feature is called "Messages in iCloud," and it relies on Apple's iCloud storage to not only back up your messages but keep an identical copy of the iMessages on your iPhone and iPad.
This is helpful for several reasons:
First, if you ever lose an iPhone you can restore it and all of your messages, down to the last one sent or received (instead of the last backup).
Second, if you delete a message on your iPhone or iPad, it'll delete from the other device. That didn't work previously, so it was really annoying to switch to an iPad only to see old conversations still floating around.
Finally, you can save a lot of local storage -- holding on to lots of iMessages can quickly add up to several gigabytes of data. Storing it in iCloud frees all of that up.
The new feature is really convenient, so I'll show you how to set it up.
It'll look like this when it's turned on:
That's all you need to do. Now everything will remain in sync across all of your iOS devices, and you'll have a backup of all of your messages in case you lose your phone.