What are your alternatives if you want to copy some files from your computer to a SharePoint library? SharePoint offers two, which is the Multiple Upload function and the Windows Explorer view.
The Explorer View offers a way to transfer your files from your computer to a SharePoint library as if you were transferring files from one folder to another. This function is extremely slow and doesn’t allow you to predefine a set of metadata on the files you are moving. If your content type in SharePoint have a required field, all your documents will be checked out under your name and you’ll need to edit every document one by one to set the missing properties. For massive files upload, it’s not rare to see a “not responding” window.
The Multiple Upload function is by far the one that I prefer. You can upload your files by selecting them from your computer and you see their status as they are uploaded. Unfortunately, you can’t copy more than 100 files at the same time and you can’t copy a folder as a single item. If you want to copy files in a folder structure, you need to recreate your folder structure in SharePoint and copy your folders content one by one. There’s no way that I know of to easily manage properties on those documents when they are uploaded.
Thanks to Sharegate, you now have a third option. With Sharegate, you can simply browse your computer and copy files or folders to a SharePoint library. As you are copying your files, you can also define a Property Template that will automatically set all your metadata to your files. You will also be able to copy more than 10 000 files at the same time without having any problems. See the My Computer to SharePoint tool for more information.

Select files and folders from your computer
Define properties for your documents

All your documents are in SharePoint now with their metadata