What is the startup setting?

You can check the startup setting:

• Edit > Preferences > General > Startup: "When Firefox Starts":
  "Show my windows and tabs from last time"

If you use "Show my windows and tabs from last time" then Firefox won't ask for confirmation. You would have to select on of the others, but note that "Show my windows and tabs from last time" is the most reliable way to make sure not to lose tabs in case Firefox doesn't close properly.

That is my start-up setting. But I'm still not getting a warning when closing multiple tabs.

I know it's the most reliable way to avoid losing tabs, but restoring tabs it not the issue here, the issue is a lack of warning when closing multiple tabs.

When session saving is enabled, Firefox will not warn when being closed. That's by design.

If your main problem is with the keyboard shortcut, there are extensions to add a warning or just disable the shortcut.

In the past if a tried to close all tabs I received a warning. Now when session savings is enabled you will not issue a warning. This is an enhancement to have me wait 5 minutes until all my tabs reload rather than give me a warning. Why was this an improvement????? Put it back the way it was or give me an option to request warning messages.

I agree with Toledo-John. In the past, I've always had BOTH "restore most recent tabs" AND "Warn when closing multiple tabs." Please let me know if there is an add-on I can install to request a warning message.

This feature change was most definitely not an improvement.

Would someone from Firefox/Mozilla post a reply or are we just talking to each other in circles. Maybe it is time to change to Chrome.