Periodic Bookmark Backup per SilverRabbit90

Periodic Bookmark Backup automatically exports your Firefox bookmarks to a standard HTML file at an interval you choose, so you always have a recent, portable copy you can re-import into Firefox or any other browser.

Features:
- Automatic backups on a custom schedule (set the interval in minutes and seconds).
- Two file modes: overwrite a single file, or keep a history with timestamped files.
- Save to a subfolder inside your Downloads folder, or enable "Ask where to save" to pick any folder through the Save As dialog.
- Optional "Include site icons": embeds each site's favicon in the file so the icons reappear when the bookmarks are imported into a fresh profile or another browser.
- Choose the icon size (16 to 64 px, default 16x16) to balance sharpness against file size.
- "Back up now" button for on-demand backups, plus a live countdown to the next automatic backup.
- Standard Netscape bookmark format - fully compatible with Firefox's own import/export.

Privacy: Your bookmarks are read locally and written to a local HTML file. The only optional network request is to DuckDuckGo's favicon service to fetch site icons (only the bookmark's domain is sent). Disable "Include site icons" to keep everything fully local.