This is because the file size is calculated based on something called “logical size” rather than “physical size”.

If you’re using online-only files with macOS 10.13 to 12.2, you may notice that online-only files appear to take up space when you try to manage storage space in your Mac settings. Still, this takes up much less space than the file itself would. Online-only files take up a small amount of space on your hard drive as the placeholder requires space to store the file name and the shortcut to. Why do online-only files take up storage space on my hard drive? Note: Files are already set to online-only by default on Dropbox for macOS 12.5 or higher. Click the dropdown next to New files default and click Online-only.Click your avatar (profile picture or initials) in the top-right corner.Click the Dropbox icon in your taskbar (Windows) or menu bar (Mac).You can make all files that you add to online-only by default: How to set files to online-only by default However, those files will no longer appear in the Dropbox folder on your computer. Selective sync also helps you save hard drive space by removing files from your hard drive so that they’re online-only. When you open an online-only file, Dropbox automatically makes it available offline again, but you can change it back to online-only at any time. Dropbox removes this file or folder from your computer’s hard drive, so that it only takes up space in your Dropbox account online. You can only open it if you’re connected to the Internet.

If you set a file or folder to online-only, you’ll still see the file or folder in the Dropbox folder on your computer, but it’s just a placeholder. This means that they take up space both on your computer’s hard drive and in your Dropbox account, but are available even when you’re not connected to the Internet. If you haven’t set a file or folder to online-only, then all files and folders in the Dropbox folder on your computer are available offline.

Click Make online-only or Make available offline.

Right-click the file or folder you’d like to set to online-only.

Open File Explorer (Windows) or Finder (Mac).

How to set a file or folder to online-only or available offline

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