Nearly a year after it was first announced, Messages in iCloud is finally available. All you need to enable it is iOS 11.4 on your iPhone or iPad, and macOS 10.13.4 on your Mac
You’ll almost certainly want to turn this feature on as it improves on the sort of half-baked syncing feature that was the only option in previous releases. Before, if you were signed into the same Apple ID on your iPhone and iPad, then the Messages apps on each device would simply show incoming messages at the same time. As you replied back and forth, each device updated the conversation threads in unison.
But this had big limitations. The devices all needed to be powered on and connected to the internet at once; if a device was offline, it wouldn’t ever get the messaging changes from your other devices. And if you deleted a conversation—say, a list of two-factor authentication codes—they would only disappear from the device you’re currently using.
Messages in iCloud fixes all that. It stores all your Messages (iMessages and SMS texts), including attachments and images, to your iCloud account and syncs them between devices. All your devices always have the most recent state. If you delete a thread, it deletes everywhere. If you set up a brand new device, it will have your entire Messages history.
And if you’re worried about security, note that Apple assures us that all your iMessages, including files and photos, are still end-to-end encrypted.
How to enable Messages in iCloud
First, you’re going to need iOS 11.4 or later on your iPhone or iPad.
In iOS beta versions prior to the release of 11.4, you would be prompted to enable Messages in iCloud the first time you opened the Messages app. Just agree, and you’re good to go. In the final iOS 11.4 release, that prompt appears to be gone—you’ll have to dig into your Settings to enable the feature.
Tap on your iCloud and Apple ID settings (it’s your name and image).
Tap on iCloud.
Toggle Messages on.
You’ll need to be plugged in and connected to Wi-Fi in order for your Messages history to sync up the first time. There may be a lot of data there, and Apple doesn’t want to kill your battery (or data plan) uploading it. After the initial sync, everything should always stay up to date as long as you’re connected to the Internet.
Enabling Messages in iCloud is a little different on the Mac.
Open the Messages app.
In the menu bar at the top of the screen, click Messages then Preferences.
Select the Accounts tab.
Choose your iMessage account in the left column.
Make sure Enable Messages on iCloud is checked.
Once this is enabled on all your devices, messages should always stay in sync, including deleted messages or threads, attachments, or images and videos.