Meld - What is Meld? Meld is a visual diff and merge tool targeted at developers.
FileZilla - FileZilla is an FTP, or file transfer protocol, client. It lets individuals transfer single files or batches to a web server. For many years, FTP was the standard for website design. Read more about FileZilla.
WinMerge - WinMerge is an open source differencing and merging tool for Windows.
WinSCP - WinSCP is an open source free SFTP client and FTP client for Windows.
Beyond Compare - Beyond Compare allows you to compare files and folders.
Cyberduck - A libre FTP, SFTP, WebDAV, S3, Backblaze B2, Azure & OpenStack Swift browser.