Transfer a large folder of photos and videos to iCloud Photos
The probably easiest way to get this done is to import the pictures into Photos.app on your Mac and let iCloud do the syncing.

Open System Preferences -&gt; Apple ID / iCloud (depends on macOS versio)
Make sure &quot;Photos&quot; has a checkmark

Then start Photos and wait for the photo library you already have to sync to your Mac (may take a while depending on the load on Apples servers, your bandwith etc). Afterwards drag&amp;drop your photos into the Photos window (or right-click on them and add them to Photos via the Sharing entry) and let the sync copy them into iCloud.
As you have already started to upload them directly to iCloud.com you may run into duplicates. Photos won't detect them, so either delete them first (in either iCloud.com or Photos) or don't reimport the photos already available in the library.