Hello, an extension that runs in private browsing windows could be problematic if it has access to information you would rather keep private. Firefox lets you decide which extensions are allowed to run in private windows. Additionally, an extension is not enabled for private browsing by default. You must grant it permission, either during installation or later through the extension's settings.

If you do not give an extension permission to run in private browsing, it should still work normally in non-private browsing, unless the extension explicitly uses features that require private browsing access (like opening new tabs in a private window). For more information visit the following link: Extensions in Private Browsing.

Hi Clement, here are some further thoughts:

The answer depends on how you use private browsing. The main difference is that Firefox doesn't record your history from private browsing windows to disk; it vanishes when you close the last private window. You can visit the sites either way, depending on how you feel about keeping traces of your browsing off your computer.

You may have noticed when you installed each add-on that Firefox would inform you of certain sensitive permissions the extension requires. You can look at those permissions in deciding which extension you want to allow in private windows -- or in any windows. For example, some extensions just look at the information on tabs -- title and URL -- while others can see everything in the page and what you do in the page. More info here: Tips for assessing the safety of an extension.

So returning to your original question, assuming you like and trust all of your add-ons, it's up to you which ones you want access to in private windows and which ones you want to exclude for whatever reason. Some people use private windows simply to avoid cluttering their browser history, and they want everything else to be the same. Others may use it for sites where there is more risk from a rogue add-on and they only want a core set to run. Each person is going to have their own approach.