We already talked about the feature here ICloud Messages, released on iOS 11.4 / macOS High Sierra 10.13.5, which allows all your conversations from iMessage definitely get saved to the cloud instead of taking up space on your devices.
The problem that some people prefer is not enabling this option: whether it's privacy related reservations or having a free iCloud plan with little space available and gigantic conversations (full of heavy media), in some cases it's a better idea to leave iCloud Messaging out about the game. In this case, when you unbox a new Mac, for example, your messages will not be automatically synced.
Fortunately, there is a way around this situation. It involves a bit of "brute force" on the part of the user, but it doesn't require any kind of witchcraft required, just that you still have your previous Mac in hand, with properly saved iMessage messages.
From the process, the following:
- On the old Mac, open the Messaging app, then your preferences with the command,.
- Enable the option “Save history when conversations are closed”.
- Turn on your new Mac and make sure both computers are connected to the same Wi-Fi network and AirDrop enabled.
- Still on the old Mac, open Finder and use shortcut G to open the "Go to Folder" screen. In it, paste the following location: / Library / Messages /; then click "Go."
- Select the entire contents of this folder by pressing A; then copy it to a new folder, which we will call here “Backup iMessage” created on the Desk (Desktop).
- Drag this new folder to AirDrop and send it to the new Mac; save it to the table.
- On the new Mac, do the same thing: Open Finder, type G and paste / Library / Messages / by clicking "Go" then.
- In the open folder, paste the contents of the “Backup iMessage” folder.
- Restart the new Mac.
Ready! Now your old Mac messages will usually appear on the new machine.
Unfortunately, there is no similar process to achieve the same effect on iOS which is natural since the mobile system does not have its library open so we can manually import the message history. Still, the tip is recorded. 😉