Duplicate files · Duplicates in cloud accounts
Why is my cloud duplicate scan taking so long?
Short answer: Your provider has to list every file, and big accounts hold a lot of them, so most of the time is spent waiting on the provider. Duplicates appear as they're found, usually within about a minute, and the files-checked count keeps rising while it works.
Because Storage Studio has to ask your provider to list every file in the account, and a large account can hold hundreds of thousands of them. Most of the time is spent waiting on the provider, not on your Mac.
You don't have to wait for the end: duplicates appear as they're found, usually within about a minute, and the list says Still scanning — more may appear. The status line keeps counting up — "Reading … — … files checked" — so you can see it's working. You can switch to other sources meanwhile; each account scans independently.