I just install the latest macOS update on my iMac. After it restarted, it showed me this:
While this is a useful feature for some people, it can be problematic, because it’s not clear which files are in the cloud and which are local. It’s very easy to accidentally delete files with this feature.
In addition, I only have 1 Mbps upload, so sending those 9 GB to iCloud would cripple my internet for a couple of days. And I recall when I accidentally turned this feature on when it was released, it was very difficult to turn it off without losing my files.
It’s a very bad idea to present this feature to users with the option checked by default. This should be an opt-in feature, not an opt-out feature. I predict that many users will run into problems with their files because they see this dialog, and click Continue without really thinking about it. They’ll see the bit about saving space, without understanding the consequences. If you haven’t updated, I recommend you don’t turn on this feature, at least not until you better understand how it works. Here’s an article I wrote when this feature was introduced.
If I were really cynical, I’d say that Apple is doing this to get people to spend more on iCloud storage…
Note: a commenter pointed out that he didn’t get this dialog when updating his Macs. I just updated my MacBook Pro and didn’t see the dialog. But it is a computer I don’t use much, and there’s not a lot of files on it. My guess is that the dialog appears if you have less than a certain amount of free space. On my iMac, with a 256 GB SSD, there’s 92 GB free (though, from day to day, for reasons I don’t understand, it oscillates from about 45 GB free to now over 90 GB). On the MacBook Pro, also with a 256 GB SSD, there’s 136 GB free.