Downloading pictures from the Cloud on to the Mac: File Duplication?

Gidget_D wrote:

... I dragged the files from the download folder over to the photos app, thinking that moved the files. But now I'm thinking it copied, rather than moved the files as they still exist in the download file (and I can see pic's in the photos app). So, my confusion is, are the files also in the photos app? Or are they referred (? not the correct word, I'm sure) to the download file. The duplicates are on the Mac, 2 locations - download file and photos app. But it's not clear to me if they are duplicate files.

...

This depends on your settings in the Photos > Settings (or Photos > Preferences in older system versions).

With Photos running go to the main menu bar, click "Photos", then "Settings". In the Settings panel ckeck the setting for "Importing". Is the checkmark still set for "Copy items to the Photos Library"?

• If this checkmark is set, Photos has copied the files into the library.
• If not, Photos is referencing the imported files in their original location in the Downloads folder. In that case select the recently imported photos and use the command "File > Consolidate" to copy them into thePhotos Library and also change the Setting for Importing in Photos. Only then delete the photos from your Downloads folder.

See: Where are the photos I imported into Photos on my Mac? – Apple Support (UK)

To see, if you are still having any referenced files that need consolidating, create a new smart album:

• File > New smart album
• Set the rule to Photo is Referenced

If this smart album is not empty, select all photos in this album with ⌘A, then use the command "File > Consolidate" to copy them into the Photos Library.

Are you connecting the iPhone to the MBP via UBB cable and importing that way. If so the normally, you wouldn't get duplicates. But some have reported that when they do it that way Photos is not detecting the previously imported photos and trying to import them again.

If that's the case then you can cull out the duplicates as follows:

You want an app that will identify the potential duplicates, put them in an album or mark them with a keyword for easy retrieval and deletion by you. You don't want one that does the deletion itself for obvious reasons. 

I've run tests on the these two apps with the following results and found them to be safe to use:

PowerPhotos - $29.95  

PowerPhotos is the iPhoto Library Manager version for Photos and is very powerful. Although more expensive I would recommend it as it has more capabilities than the others like the capability to merge Photos libraries or copy photos, both original and edited versions, along with their metadata between libraries.

PhotoSweeper - $9.99 - Demo version available.

PhotoSweeper compares bitmaps and/or histograms so it can detect duplicate images even if they have different file sizes, file names, image sizes and capture dates.

There's another way to sync the library on your MBP with you iPhone automatically and that's with iCloud Library. You'd have to purchase enough iCloud Drive space to house the combined libraries of both your iPhone and MBP. You might have to set both devices to Optimize Storage in order to store all of the photos.

Please read the following user tip and restate your question/problem in detail: 

     Writing an Effective Apple Support Communities Question - Apple Community

What system and Photos versions are you using?

What Mac model and year are you using?

Where are you downloading from?

What format are the photos?