Session Vault for Firefox by UncleVictor

Session Vault keeps copies of your workspace so that a crash, a wrong click or a failed session restore never costs you your tabs.

What it does
- Daily (or weekly) backups, plus an autosave a minute after your tabs change.
- Tab-drop guard: when many tabs disappear at once, the copy made before that is kept until you say everything is fine.
- Each copy keeps windows, tab order, the active tab, pinned tabs, tab groups (name, colour, collapsed), titles and containers.
- Restore into new windows, or replace the current session. Before a replace a safety copy is saved, and old windows close only after everything was restored.
- Copies are verified with a checksum before older ones are removed. Smart retention: your newest copies, the best copy of every day and week, pinned copies, and a trash for 7 days.
- Copies are also written as JSON files to your Downloads folder, so they survive a reinstall. Import them back, or import Firefox's own session files (sessionstore.jsonlz4, recovery.jsonlz4, previous.jsonlz4, upgrade.jsonlz4-*), optionally with recently closed windows, tabs and saved groups.
- Search across all copies; click a saved tab to open it.

Privacy
No network requests, no analytics, no cloud. Everything stays in your Firefox profile and your Downloads folder. Private windows are never saved.

Limits set by Firefox
Closed and saved tab groups are not visible to extensions; split views and back/forward history cannot be restored; about:, file: and data: pages reopen as a placeholder page that shows the original address.