I found out what I was doing wrong. If you are in a private window, you can only open into a private window. In a non private window you can open into a private or non private window.

I closed the Private Browsing window and then the non-private window showed up under file, but immediately reverted to private browsing. Now what?

Hi ddartist, it is possible to start Firefox automatically into private browsing mode with no non-private windows. Are you maybe doing that? Check out the last section of this article Private Browsing - Use Firefox without saving history ("How do I always start Firefox in Private Browsing?").

Future Firefox versions will support Private Browsing per tab, this is already available as an extension.

• Private Tab: https://addons.mozilla.org/firefox/addon/private-tab/

The Firefox menu button gets a purple background or you get a purple PB mask on the menu bar or tab bar (Linux) when you are in a PB tab and all Private Browsing mode tabs get a dashed underlining unless you are in permanent PB mode.

You can switch a tab to private mode and to normal mode via the right-click context menu of the tab bar.