In Preferences - Backup you will find the text entry fields "Exclude files matching wildcard" and "Exclude folders matching wildcard". You can use them to exclude any files or folders which match a specific wildcard.
EXCLUDING FILES MATCHING WILDCARD
Here you may specify wildcards to exclude files. For example:
*.tmpwill exclude all files with the extension .tmp. These are usually temporary files that don't need to be backed up.
~$will exclude all files with names that begin with ~$. These are temporary Microsoft Office files that don't need to be backed up.
desktop.iniwill exclude all files named exactly "desktop.ini`. These are system files on Windows that don't need to be backed up.
EXCLUDING FOLDERS MATCHING WILDCARD
Here you may specify wildcards to exclude folders. For example:
*example*will exclude the folder /a-example-b/.
example*will exclude the folder /example-name/.
Exclusions only apply to files and folders that have not been backed up yet. If you have already backed up a file or folder, it will continue to upload even if a subsequently created exclusion would have otherwise excluded it.
The wildcard patterns that are accepted are those implemented by Python's fnmatch package.
Wildcards cannot include slashes, backslashes, or full paths. For example, the exclusion
*about* will exclude /aboutme/, but it will not work if you include slashes such as
/*about*/. Because slashes and backslashes cannot be included, full paths will not work. If you want to exclude a particular file or folder, the easiest way to do so is to open the Backup tab and deselect it there.
Exclusions are global. For example, if you exclude PDF files with
Multiple exclusion rules may be placed on a single line, separated by a comma and a space:
Alternatively you can place each exclusion rule on its own line: