When you change your Mac or do a clean install on your current machine, virtually all information (contacts, appointments, reminders, notes, emails, photos, etc.) is automatically transferred to your computer as soon as you type your email and password your Apple ID. This is a hand in the wheel, since the most sensitive information linked to your account will always be available very easily (without the need for a backup restoration, for example).
However, something that I also consider essential in the Apple ecosystem but that is not automatically transferred along with this other information for reasons involving security, the message history (iMessages), present in OS X since version 10.8 (Mountain Lion).
But know that doing this is not very difficult / complicated. Of course, if you do a backup via Time Machine, all of that information will be saved in good time. But if your idea starts with a new, zeroed system (either by changing your Mac or reinstalling it, as I mentioned above), it makes no sense to rescue a Time Machine backup
Below, I'll show you how to download the message history:
- Before changing Macs or reinstalling the system, open the Messages app and go to his preferences (Messages Preferences; or by shortcut ,).
- Under "General", check the "Save history when conversations are closed" option.
- Now click on the Finder icon, go to the "Go" menu and choose the "Go to Folder" option.
- Type ~ / Library / Messages and click on the "Go" button.
- You will then see the folders / Archive / (which keep your messages in conversations already closed / saved) and / Attachments / (which stores all the images, videos and files you exchanged in those conversations), in addition to files called chat.db ( they keep the information / history of the messages that are still active).
- The size of these folders can vary depending mainly on the number of attachments you have; if everything is reasonably sized, copy these files to a USB stick, external HDD or cloud storage service of your choice.
- Everything duly saved, on your new Mac (or on your current Mac with the system installed from scratch) repeat the process by going to "Go", choosing the option "Go to Folder" and typing ~ / Library / Messages.
- Transfer the copied files to the location and then restart your Mac.
Okay, now when opening the Messages app everything should be there!