Firefox can restore all windows and tabs that were open when it was last closed or terminated unexpectedly. This article describes the circumstances under which Firefox will restore your previous session and how you can configure it.

When session restore occurs

When you select Restore Previous Session from the default home page

If you had tabs and windows open when you last closed Firefox, the default Firefox home page will have a Restore Previous Session button on it. To get your tabs and windows back, just click it.

When you select Restore Previous Session from the History menu

Here's how to get your tabs and windows from a previous session back if you don't use the default Firefox home page:

After installing an add-on

When a new extension or theme is installed, you must restart Firefox to enable the new add-on. To restart, click Restart Now. All windows and tabs are re-opened when Firefox restarts and installs the new add-on.

After a software update

To apply any updates to the Firefox application that have been downloaded, you must restart Firefox. To restart, click Restart to UpdateRestart Firefox to Update.

After restarting with add-ons disabled

When you restart with add-ons disabled to troubleshoot Firefox problems, your tabs and windows will be reopened.

After a crash

Due to unexpected issues such as problems with a website, software errors, or an accidental loss of power, Firefox may unexpectedly close. In these situations, Firefox can restore the pages that you were visiting when it is restarted. Firefox will automatically restore your previous session, the first time you launch it after a crash.

If Firefox crashes a second time, the Restore Session (i.e. "Well, this is embarrassing") page will appear when you next launch Firefox.

• To restore your previous session, select the windows or tabs you want to restore and click Restore.
• If Firefox continues to experience errors when windows and tabs are re-opened, you can launch Firefox without restoring these items. Click Start New Session.

When you've set Firefox to show your windows and tabs from last time

You can set Firefox to always show your windows and tabs from your previous session each time you start Firefox. To change your Firefox startup settings, see Configuring session restore, below.

Configuring session restore

By default, when Firefox starts, a single window is opened, displaying your specified home page. If you wish, you can configure Firefox to open all windows and tabs from your previous session:

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.
2. Select the General panel.
3. From the When Firefox starts drop-down, select Show my windows and tabs from last time.
4. Close the Settings page. Any changes you've made will automatically be saved.

Privacy issues

Session Restore may keep you logged in to sites that you were logged into before you closed Firefox. If someone else used your computer after you, they could access your account on these sites. If this is a concern then you should not configure Firefox to open all windows and tabs from your previous session.

You may also wish to disable the Session Restore crash recovery feature which is enabled by default. This will prevent restoring a previous session when Firefox is opened after an unexpected close or software crash:

1. Type about:config in the address bar and press EnterReturn.
   A warning page may appear. Click Accept the Risk and Continue to go to the about:config page.
2. In the Search box at the top, type browser.sessionstore.resume_from_crash.
3. In the resulting grid, double-click on browser.sessionstore.resume_from_crash to set it to false.

Troubleshooting

Previous session not correctly closed

To get your tabs and windows back from a previous session, you should close Firefox from the menu: Click the Firefox menu and select Exit.Click the Firefox menu at the top of the screen and select Quit Firefox.Click the Firefox menu and select Quit. If you close each window or tab, only the tabs in the final window that you close are available when you restart Firefox.

Settings may be incorrect

For other session restore problems, you may need to make corrections to your Firefox settings:

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.
2. Select the Privacy panel and make sure Firefox will: is set to either Remember history or Use custom settings for history.
   • If Firefox will: is set to Use custom settings for history then make sure that Permanent Private Browsing mode is not selected.
   • If Firefox will: is set to Use custom settings for history and Clear history when Firefox closes is selected, then click the Settings button and make sure that Browsing History is not selected.
3. Close the Settings page. Any changes you've made will automatically be saved.

Based on information from Session Restore (mozillaZine KB)