Folders Start Page keeps your shortcuts, folders and settings in Firefox's storage on your computer. If you use Firefox Sync, Firefox also copies them to your Firefox account; you can switch this off in the add-on's Customize > Backups and history.

The add-on has no server, collects no analytics and never reads cookies. Its own requests carry no cookies, and it contacts others only as follows:

1. Your shortcuts' sites, for their icons: the icon files, and the main page for the
   icons it names. This happens when a shortcut has no icon kept yet or you refresh one,
   and at most once a day for one still without an icon. An icon URL you set for a
   shortcut is downloaded when you save it, to check that it loads, and kept.
2. An icon service you choose (DuckDuckGo or Google): off unless you choose one and
   allow "browsing activity" in Firefox's consent prompt. It is told the domain (such as
   example.com) of a shortcut whose site gives no usable icon, never the full address. Its
   own privacy policy applies.
3. Your search engine's suggestion service: off unless you switch it on and allow
   "search terms" in Firefox's consent prompt. What you type is sent as you type, as
   Firefox does, except text that would open as a web address. The engine's privacy policy
   applies.
4. A picture you link as a wallpaper or logo, and a search engine's icon given as a web
   address: each downloaded once and kept.

If you switch off the add-on's access to all websites in about:addons, icons it can't download are shown straight from their sites, as a web page shows images, with those sites' cookies.

Firefox's prompt reads "Share browsing activity with extension developer" (or "search terms"), its wording for every add-on. Here the data goes only to the icon service or search engine you chose; the developer receives nothing.

You can withdraw either consent in about:addons, under the add-on's "Permissions and data". When nothing uses a consent, the add-on gives it back.