History is used by the browser to enhance your experience on the Internet. When the browser remembers a website you previously visited or the username and password for your favorite web site, this information is considered your history.

However, there may be times when you do not want other users of your computer to see or access such information. For example, if a friend or family member shares your computer, you might prefer for them not to be able to see what websites you've visited or what files you've downloaded.

Firefox 3.5 and later provide "Private Browsing", which allows you to browse the Internet without Firefox saving any data about which sites and pages you have visited.

What Private Browsing will not retain

• Visited pages: No pages will be added to the list of sites in the History menu, the Library window's History list, or the Awesome Bar address list.
• Form and Search Bar entries: Nothing you enter into text boxes on web pages or the Search bar - add, change and manage search engines on Firefox will be saved for Control whether Firefox automatically fills in forms.
• Passwords: No new passwords will be saved.
• Download List entries: No files you download will remain in the list in the Where to find and manage downloaded files in Firefox after you turn off Private Browsing.
• Cookies: Cookies are file​s created ​by websites​ that​ store information ​on your​ computer​, such​ as your​ preferences ​when​ visiting​ a certain site​. These will​ not ​be stored. For more information on cookies, see Cookies - Information that websites store on your computer.
• Web cache files: No temporary Internet files or cached files from web pages will be saved until you turn off Private Browsing.

Turn on Private Browsing

1. Click on the Tools menu and select Start Private Browsing.
   
   

1. The first time you turn on Private Browsing, Firefox will alert you that it will save your current windows and tabs for after you finish using Private Browsing. Click on Start Private Browsing to continue.
   
   
   • Put a check mark next to "Do not show this message again" if you do not want to receive this alert the next time you turn on Private Browsing.
2. You will then enter Private Browsing mode, and the Private Browsing information screen will appear.
   
   

When browsing in Private Browsing mode, the Firefox window's title will show (Private Browsing) during your session.

Turn off Private Browsing

1. Click on the Tools menu and select the Stop Private Browsing entry.
   
   
2. The windows and tabs you were using when you enabled Private Browsing will appear, and you can use Firefox normally. The Firefox window's title will no longer show (Private Browsing) when Private Browsing is off.

Always start Firefox in a private browsing session

There is a setting in the OptionsPreferences window which will automatically enable Private Browsing whenever you start Firefox.

1. In the Menu bar at the top of the screen, click Firefox and then select Preferences or Settings, depending on your macOS version.Click the menu button and select Settings.

Select the Privacy & Security panel and go to the History section.

1. Click to select Automatically start Firefox in a private browsing session.
   
   
2. Close the Settings page. Any changes you've made will automatically be saved.