Practical guide
Closing a Private Window Does Not Remove Downloads
Remember the files created during a private session, especially when you use a shared device.
Separate a browsing session from a saved file
A private window can change what the browser retains about a session, but a downloaded file is a separate object. Mozilla explicitly states that files downloaded during Firefox Private Browsing remain saved on the computer. That distinction matters if you download an account export or a private document and then close the window expecting the task to disappear. Decide whether the file should be created on that device before using the download button, not after relying on the window's privacy label.
Consider the shared-computer example
Suppose you borrow a laptop to retrieve a document, use a private window, and finish by closing it. The document may still be available wherever you chose to save it. The device owner did not need to watch the browser session to encounter the resulting file later. A better approach is to avoid downloading sensitive material on a borrowed machine unless it is necessary and you understand how it will be handled. The window mode does not take responsibility for that decision.
Track what you intentionally created
Keep a brief mental or nonsecret list of the outputs from the task: one downloaded archive, one printed page, or a document opened in another application. Account for each output before you consider the visit finished. Do not open unrelated folders or erase material you do not recognize in an attempt to clean everything. Stay within the files and actions you created. If the device is not yours, agree with its owner on a suitable handling method rather than making broad assumptions about its storage.
Use privacy labels precisely
When explaining your setup to someone else, avoid saying Private mode saves nothing. A more useful description names the particular behavior you checked and its limits. For your own routine, treat a download as a separate privacy event with a destination, contents, and retention decision. If you no longer need the material, use the device's normal file-handling process, understanding that backups or other copies may require separate review. The takeaway is practical: closing a browsing session is not the same action as accounting for its outputs.
Sources checked
Linked reference pages checked on 2026-09-09. Product details can change. No paid-membership test or sponsorship is implied.
Mozilla: Private Browsing and saved downloads ↗