5 Messages on iCloud
In iOS 11, you can upload your iMessages and attachments to iCloud to save space on your iPhone. It also means that the service will be more reliable as you won’t lose your messages when you switch to a different device or restore it. All your iMessages will get backed up and synced to iCloud automatically.
Once your messages and attachments such as photos and videos have been saved in iCloud, you can remove the old ones from your device. They will remain in the cloud and you can view them anytime by simply scrolling up in a conversation to load them.
As of now, Apple has removed the Messages on iCloud feature. It was removed in iOS 11 Beta 5, but Apple says that it will be back in the future, possibly after iOS 11 is officially released to the public.