Importing sessions from other extensions

Tab Session Garrison reads four session file formats. Imported sessions are added to your list — nothing already saved is replaced or overwritten.

How to import

Open Settings → Sessions (the gear icon in the popup, then Sessions)
Under Import, choose one or more files — several at once is fine
Each file is listed with its status; click Save to commit the import

Supported formats

Source	File	Where to find it
Tab Session Garrison Tab Session Manager	`.json`	Exported from Settings → Sessions → Export, or an automatic backup from the backup folder
Session Buddy	`.json`	In Session Buddy, use its export command and choose the JSON format (not CSV or HTML)
Session Manager (legacy Firefox add-on)	`.session`	The add-on’s `sessions` folder inside your old Firefox profile
Firefox Session Store Backup	`.jsonlz4` `.baklz4`	The `sessionstore-backups` folder in your Firefox profile — see below

Finding Firefox’s own session store backups

Firefox continuously writes its current window/tab state to compressed files in your profile. These are the last resort when a crash or a bad restart lost your windows.

Open about:profiles
For the profile you use, click Open Folder next to Root Directory
Open the sessionstore-backups folder

You will typically see:

recovery.jsonlz4 — the most recent state Firefox wrote
recovery.baklz4 — the previous copy of the above
previous.jsonlz4 — the state from your last Firefox session
upgrade.jsonlz4-20211001010123 — a snapshot taken before a Firefox update

Copy the files somewhere else before importing rather than picking them out of the live profile folder — Firefox rewrites them while it’s running.

Formats that are not supported

OneTab, browser bookmark exports (.html), and plain lists of URLs won’t import through the session importer. For a plain list of URLs, use Settings → Sessions → Import URL list instead, which builds a session from one URL per line.

Troubleshooting

The file imports but produces no sessions

The importer identifies a .json file by its internal structure, not by its name. If a file is valid JSON but matches neither the Tab Session Manager nor the Session Buddy layout, it is skipped silently. Re-export from the source extension and pick its native JSON format.

The file is rejected outright

Check the extension is one of .json, .session, .jsonlz4 or .baklz4. Compressed archives (.zip) must be unpacked first.

Imported sessions have the wrong date

Formats other than Tab Session Manager’s carry limited metadata. Where a source file has no timestamp, the import time is used instead.

Duplicates after importing

Importing the same file twice creates a second copy of each session — the importer does not de-duplicate. Use multi-select in the popup (Ctrl-click, Shift-click, or the keyboard) and delete the extra copies in one action; a single undo brings them all back if you overshoot.

Still stuck?

Open an issue with the source extension, its version, and the file extension you tried.