What format are the Backups? JSON? XML?

There are 3 types of data backups to ensure your data is safe:

On paid plans:

1)Automatic internal system backups which go back X number of days based on the plan you have purchased.

2)Manual (user initiated) - Full backup to JSON file. This backup is executed by right clicking the Bookmarks folder and selecting "Export".

On all plans:

3)Manual (user initiated) - Copy URLs to clipboard feature which can be saved to a text file to backup your bookmarks manually. It is a list of folders, sub folders and URL, but no creation dates, or supplementary data like in the JSON file above).

The image below shows the "Export" and "Copy URL" menu items in TabsFolders: