How separate do you want to keep the data? I ask that because if you have two Mozilla accounts, sign out of your personal Mozilla account and then sign in to your business Mozilla account in the same Firefox profile, your data from both will end up getting merged by Sync. Sync combines selected local data with your account data. ''Assuming you want complete separateness:'' Firefox has a new profiles feature that is part of a progressive rollout which makes it difficult to cause data mixing. See: [[Manage Firefox profiles]]. Since I have not tested that feature myself, I will give the old school method ([[Profile Manager - Create, remove or switch Firefox profiles]]). Either way, the first step is the same: (1) Using https://accounts.firefox.com/settings remove the business address from your personal account ([[Add a secondary email address to Mozilla accounts]], except in this case you'll be removing it) (2) Create a new business profile and do not sign it into an account just yet (detailed steps below) (3) Assign the business profile a different toolbar theme so it is easier to spot the difference when switching windows ([[Use themes to change the look of Firefox]]) (4) Use your business email to create a new Mozilla account through the business profile ---- ''Note: the following guide uses the "old" profile manager rather than the newer graphical interface since I haven't tested the new one.'' '''Second Profile Setup''' Inside Firefox, type or paste '''about:profiles''' in the address bar and press Enter/Return to load it. Take a quick glance at the page and make a mental note of which Profile has this notation: '''This is the profile in use and it cannot be deleted.''' That is your current default profile. Click the "Create a New Profile" button, then click Next. Assign a name like ''business'', ignore the option to relocate the profile folder, and click the Finish button. Firefox will switch your default profile to the new one, so first decision: which profile do you want to start automatically when you use the main Firefox icon (this also is the profile that will be used for external links in other applications). Click the '''Set as Default Profile''' button for that profile to avoid an unwanted surprise at your next startup. '''Starting Firefox in Your Second Profile''' Scroll down to ''business'' and click its '''Launch profile in new browser''' button. Firefox should open a new window that looks like a brand new, uncustomized installation. (Your existing Firefox window(s) should not be affected.) Please ignore any tabs enticing you to connect to a Sync account or to activate extensions found on your system to avoid data crossover. It's also possible to create a desktop shortcut to start Firefox in this profile directly without going through the About Profiles page. This typically involves the following steps: * right-click a blank area of the desktop > New > Shortcut * enter the command line, typically something like this on Windows:<br><br>"C:\Program Files\Mozilla Firefox\firefox.exe" -P "business"<br><br>(Assuming you installed from Mozilla's site, not the Microsoft app store) * click Next and assign a useful name like ''Firefox business'' then click Finish