Open-source
Cyberduck: A Free cloud file browser for Windows and macOS
Cyberduck is an open-source (Libre) cloud and server storage browser, that helps you mount, access and browse your remote file without any complex configuration or setup. Currently, Cyberduck is available for Windows and macOS. Cyberduck supports FTP, SFTP, WebDAV, Amazon S3, Backblaze B2, Microsoft Azure, OpenStack Swift, OneDrive, Dropbox, and