There’re situations when it’s not enough to have documents in a single library. You might need to share a copy with your colleagues, create a backup elsewhere or just archive the old files to a different library.
Which option is the best for you depends on your specific situation. Where do you want to copy the files? Which SharePoint experience is used on the libraries? How many files do you need to copy?
Between SharePoints of different organizations
This is not what SharePoint was designed for. You have to manually download the files from your library to your local drive and then upload them to the other library.
In Classic experience this can be simplified by using the Open in Explorer functionality, reducing it to ‘drag and drop‘ work.
In Modern experience Microsoft disabled the Open in Explorer function. You’ll have to do the download and upload using the web browser interface.
SharePoint in the same organization, Classic experience
If you’re still using the Classic experience, or if you’re able to switch to it, you can use the same Open in Explorer functionality from here.
It’s a good option no matter how many files you need to copy.
SharePoint in the same organization, Modern experience
Modern experience removed possibility to open the libraries in File Explorer. But it added Copy to functionality directly into the web browser interface, as you can see here.
Good choice if you need to copy a small amount of files. You can’t use drag and drop but you’ll manually select the files you want to copy.
SharePoint in the same organization + Power Automate
Power Automate enables you to automate some of the manual work and let the platform do it for you. A simple Power Automate flow can take all documents in your library and copy them to another library.
If you need to copy the files more often or if the library contains lots of documents, the time spent on building such a flow will pay off in the future.