This is what you see when launching Private Browsing in Firefox:

Firefox clears your search and browsing history when you quit the app or close all Private Browsing tabs and windows. While this doesn’t make you anonymous to websites or your internet service provider, it makes it easier to keep what you do online private from anyone else who uses this computer.

It then links to this Mozilla Support article:

Private Browsing is a useful feature of Firefox, but only if you understand the protection it offers. It helps you obscure your online activity from other people who use Firefox on your computer, but does not make you invisible online.

They list these common myths about Private Browsing mode:

  1. It makes you anonymous on the internet.
  2. It removes all traces of your browsing activity from your computer.
  3. It doesn’t display any browsing history.
  4. It will protect you from keystroke loggers and spyware.

It’s telling that these facts needed spelling out. It’s perfectly reasonable for a layperson to expect a Private Browsing mode to be private, regardless of technical limitations or considerations.

I was worried when such modes were added to all the major browsers, not least Firefox. We’ve seen the stories of people being lulled into a false sense of security thinking their browsing was private when leaking information, or browsing nefarious sites that end up stealing their identities and money.

I’m glad to see information like this directly linked from Private Browsing mode in Firefox, but still people aren’t heeding the warnings. It was inevitable; we’ve been trained by visual onslaughts and bad UI design to dismiss dialogue boxes with the most cursory of glances. It’s why, for all Microsoft’s best intentions, those Cancel/Allow messages in Vista were an abject failure.

I still think we should do away with the name entirely and call it Sandbox Mode, or something more generic that someone without an engineering or IT background would understand.

Update: I went back to my Mac and checked what Safari says. It spells out clearly what Private Browsing mode does when you launch it:

Safari will keep your browsing history private for all tabs in this window. After you close this window, Safari won’t remember the pages you visited, your search history or your AutoFill information.