Firefox extensions store data in the browser's local storage. If you uninstall an extension, what happens to that data? Here is a clear explanation.
How Firefox extension storage works
Firefox provides each extension with an isolated storage namespace using the browser.storage.local API. Data stored here:
- Is specific to that extension (other extensions cannot access it)
- Persists between browser sessions
- Survives browser restarts and updates
- Is stored on your machine (not in the cloud)
What happens when you uninstall
When you uninstall a Firefox extension, the extension's storage data is deleted. Firefox removes the extension's isolated storage along with the extension itself.
This means:
- Habit Tracker: your habit log is deleted
- Daily Planner: your task list is deleted
- Tab Manager: your saved sessions are deleted
- Speed Dial: your shortcuts and icons are deleted
- Quick Calculator: your calculation history is deleted
Exceptions
Some extensions store data outside the browser's extension storage:
- Extensions that sync to a cloud account: your data may persist in the cloud even after uninstalling
- Extensions that write to your filesystem: files they created remain until you delete them
The extensions in this series store data exclusively in Firefox's local extension storage — which means uninstalling removes the data.
How to back up data before uninstalling
Most of the extensions in this series do not have built-in export:
What you can do before uninstalling:
- Take a screenshot of your habit grid (Habit Tracker) to preserve your history
- Copy and paste your task list (Daily Planner) to a text file
- Note your saved session names and their tab URLs (Tab Manager)
- Screenshot your Speed Dial layout
What about reinstalling?
If you uninstall an extension and reinstall it, you start fresh — previous data is not restored. This is because Firefox deletes the storage on uninstall.
What happens on Firefox update or profile reset?
Firefox update: Extension data is preserved. Normal browser updates do not delete extension storage.
Firefox Refresh (reset to default): This deletes extensions and their data. It is equivalent to a fresh Firefox installation.
Firefox profile deletion: Deletes all data for that profile, including extension storage.
Summary
If you uninstall a Firefox extension, its local storage is deleted. Back up important data (screenshots, notes) before uninstalling any extension that holds data you care about.
The 11 Firefox extensions in this series store data locally — see the full series.
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