Can I use iCloud for offline archive?

I want to take about 50 Gb of files off my computer but have them stored in iCloud. (I will also keep a local offline hard drive archive of the same files – the iCloud piece is to give me an additional copy offsite in case of disaster like my house burning down.)

Try as I might, iCloud's basic functional model and the meanings of the host of status icons in the iCloud Drive finder windows have eluded me. It's still just not clear how I can designate an iCloud folder to not sync to any local copy on my Mac like the local iCloud Drive folder.

I will also want to continue to use iCloud's synch services to maintain local and cloud copies of other files such as those created in select applications and specified in the iCloud settings panel. So, a separate use case from my offline archive needs, and one that seems to be iCloud's default so no need for help on that. I just mention it for clarification in case iCloud will do manually manage offline archive OR automatic synching but doesn't provide for both on one Mac.

All the info I find on how iCloud works seems to cover the common backup/synch use case, but not the archive use case I also need.

I would love to find a clear, simple abstract of what iCloud's file handling model itself is, so that I could infer from that whether my offline archive use case is possible. No love on that front, so I'd be happy to find just an explicit description of how to do offline archiving instead.

iCloud Drive is not intended for your use case of archiving specific files that you do not want on your local drive. Note also that iCloud Drive is not a backup solution at all. For backup purposes I would strongly suggest using an actual backup service or "raw" cloud storage (such as S3, B2 or similar).

You can open System Preferences > Apple ID > iCloud and enable Optimize Mac Storage, which will remove files from your local drive, while keeping them in iCloud Drive, when you run out of disk space. However, you cannot decide when, which files or anything like that.

For cloud archival storage, I would look at services such as S3, B2 and the like (depending on the size of your archives). For long-term storage where you will not need frequent access to the data, you can get fairly cheap storage with a service such as Amazon S3 Glacier.

I would recommend using the program rclone to copy files to S3/B2 storage (and in general to download and manage the files afterwards). It seems to always work very reliably, whereas I have found several GUI tools to be a bit wonky in practice.