I need a way to find duplicate files for those files in folders that are ONLY online in Dropbox, i.e., those that are Selectively Synchronized so they don't exist on my local computer.
I have 850,000 files on Dropbox and I need to find and delete duplicates in an easy to use manner. The earlier "solution" of using 3rd party tools to find duplicates of files in the Windows File System is not a good approach at all. Using the Windows File System requires a (potentially lengthy process) to copy all folder down from Dropbox, and then run the Third-party tool to find duplicates, deal with the duplicates, and then resynchronize the Dropbox File System and the Windows File System.
Heavy Dropbox users with a lot of files need something better !!
Dropbox Smart Sync allows you to sync just the folder and file structure to my desktop without the actual file content. The sync should be done fairly quickly. Afterwards, you may make use of 3rd party tool to help you perform the deduplication process. Though the effectiveness really depends on how the 3rd party tool performs.
If you're using a third-party tool against the local Dropbox folder, when the compare process runs it will attempt access the online-only files which will trigger Dropbox to download them back to the computer, defeating the purpose of Smart Sync.
There really isn't a viable way to run deduplication locally against files that are only stored within Dropbox. You'll need to find a third-party tool that uses the Dropbox API to access your files directly. Do a Google search for "cloud duplicate finder" and you'll find some options that may work. Just know that third-party apps are not supported by Dropbox. If you have any issues, you'll need to contact the developer.