“Failed to load sessions” — the IndexedDB error

Tab Session Garrison keeps every saved session in your browser’s IndexedDB storage. If it can’t open that database, the popup shows an error instead of your session list. This page walks through the causes, cheapest fix first.

Your sessions are almost certainly still there. This error means the database could not be opened — not that it was erased. Work through the steps below before reinstalling or clearing any storage, because some of those actions will delete your sessions for real.

1. Reload the extension

The error panel has a Reload extension link. Click it. If the database was temporarily locked — for example another Firefox window was mid-shutdown when the popup opened — this is all it takes.

2. Restart the browser

Fully quit and reopen Firefox (not just close the window). This releases any stale lock on the profile’s storage and clears the most common transient failure.

3. Check that you are not in permanent private-browsing mode

Firefox blocks persistent extension storage when history is disabled, which makes IndexedDB unavailable. Check:

Open about:preferences#privacy
Under History, if the mode is Never remember history, switch it to Remember history (or Use custom settings with Always use private browsing mode unchecked)
Restart Firefox

Note that this is a per-profile setting — a normal window in a profile configured this way is still effectively private.

4. Check that IndexedDB is enabled

Open about:config and accept the warning
Search for dom.indexedDB.enabled
It must be true. If it’s false, double-click to flip it, then restart Firefox

5. Check that site data isn’t being cleared on exit

Privacy settings and cleanup extensions that wipe cookies and site data can take extension storage with them. In about:preferences#privacy, look at Cookies and Site Data → Delete cookies and site data when Firefox is closed. If it’s on, and you also run a cleaner add-on (Cookie AutoDelete and similar), try disabling that cleanup temporarily to see whether the error stops recurring.

6. Check disk space and profile permissions

IndexedDB fails to open when the volume holding your Firefox profile is full or read-only. Free up space, then restart. You can find the profile folder via about:profiles → Root Directory → Open Folder.

7. If the error persists: rescue your data first

Only at this point consider clearing storage or reinstalling — both destroy saved sessions. Before you do either:

If the popup ever loads: open Settings → Sessions → Export and save the .json file somewhere outside the profile.
If it never loads: check for automatic backups. Their folder is set in Settings → Backup, and defaults to Tab Session Garrison - Backup inside your downloads folder. Those .json files can be imported later.

With a copy in hand, remove and reinstall the extension, then re-import through Settings → Sessions → Import. See Importing sessions for the supported formats.

Still stuck?

Open an issue with the browser version, the exact error text, and anything from the Browser Console (Ctrl+Shift+J) at the moment the popup fails: report it on GitHub.