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I updated my computer for the first time since downloading Firefox, and somehow this caused Firefox to completely reset.

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I started using Firefox for the first time last week and yesterday I decided to update my computer (Mac OS Catalina 10.15.4), and once the update was finished I saw a ? instead of the Firefox icon. I was still able to open the app, but it was as if everything was completely reset. "Welcome to Firefox" page, had been signed out of my account -- and even when I signed in, I got an email that a "new" device was logging in, and my entire account had been wiped of all extensions, bookmarks, settings, etc.

Thankfully, I was able to recover an older version of my profile to replace the deleted bookmarks, browser history, and most (but not all) of my settings -- but I absolutely do not want this to happen every time I update my computer, and I don't even understand why this happened in the first place. No browser I've ever used has just erased all my data and history when all I did was install a minor update to my OS. Not a great first impression tbh, but if I can prevent it from ever happening again that would help.

Chosen solution

A common mistake that a lot of Mac users make is that they run Firefox directly from the ****.dmg file that they download instead of copying the firefox.app file into the applications folder on their device. See How to download and install Firefox on Mac for more information.

Running right from the DMG file makes a virtual disc, which can cause the type of issue that you have described when updating or even just closing Firefox. This is an issue because the location of the Firefox program can change when you are running using the DMG file, which tricks Firefox into thinking that it's a new installation.

For a new installation, Firefox is designed to create a new blank profile for you, making it appear as though the browser has been reset and all information has been erased.

Fortunately, as it sounds like you've already discovered, recovering the old information is not typically a difficult process. It involves going to the about:profiles page in Firefox and then setting the default profile back to the original profile so that Firefox opens that profile whenever it opens.

However, continuing to run from the DMG file will cause the same issue to occur. Running Firefox from the firefox.app file after it's copied into the applications folder should stop the issue from happening.

As a side note, when you copy the application into the folder and launch Firefox from it, a new profile will again be created for you because the Firefox location has changed. You can recover the profile again using the steps described above.

Hope this helps.

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Chosen Solution

A common mistake that a lot of Mac users make is that they run Firefox directly from the ****.dmg file that they download instead of copying the firefox.app file into the applications folder on their device. See How to download and install Firefox on Mac for more information.

Running right from the DMG file makes a virtual disc, which can cause the type of issue that you have described when updating or even just closing Firefox. This is an issue because the location of the Firefox program can change when you are running using the DMG file, which tricks Firefox into thinking that it's a new installation.

For a new installation, Firefox is designed to create a new blank profile for you, making it appear as though the browser has been reset and all information has been erased.

Fortunately, as it sounds like you've already discovered, recovering the old information is not typically a difficult process. It involves going to the about:profiles page in Firefox and then setting the default profile back to the original profile so that Firefox opens that profile whenever it opens.

However, continuing to run from the DMG file will cause the same issue to occur. Running Firefox from the firefox.app file after it's copied into the applications folder should stop the issue from happening.

As a side note, when you copy the application into the folder and launch Firefox from it, a new profile will again be created for you because the Firefox location has changed. You can recover the profile again using the steps described above.

Hope this helps.