A "File already exists" dialog will appear. Choose Resume and click OK. FileZilla will then check the existing file size and issue a REST command to fetch only the remaining data. Automating the Resume Action
To avoid the manual pop-up every time a transfer fails, you can configure FileZilla to resume automatically:
If your connection drops or you accidentally close FileZilla, you can manually trigger a resume:
Interrupted downloads are a common headache when transferring large files, but FileZilla provides several ways to continue where you left off without losing progress. How to Resume an Interrupted Download
If you only want this behavior for your current session, navigate to Transfer > Default file exists action... and make the change there. Handling Failed Transfers in the Queue
Go to Edit > Settings > Transfers > File exists action . Under "Downloads," select Resume file transfer from the dropdown menu and click OK.
How to permenantly enable 'resume' download/upload function?