Of the two big browsing features of 2008, one seems to run counter to where developers are driving their browsers. The melding of the location bar to the search bar was expected in Firefox and Opera, thanks to beta versions. Chrome has it, too, calling it the Omnibar. What seems to have caught developers off-guard has been the clamor for a universal switch to stop the cache and browsing history from recording anything at all.
Microsoft's InPrivate debuted in Internet Explorer 8 beta 2, and Google Chrome's version is the well-received Incognito feature. So far, in Firefox, the feature has only been available via the Stealther plug-in, which basically copies all the features of InPrivate except that you don't have to open a new browsing window. Now, Mozilla has announced through the Firefox 3.1 status tracker that a privacy toggle will be a baked-in feature.
It turns out that Mozilla has had such a toggle on its radar since 2004, when Apple's Safari introduced a cache-avoiding browsing session. So what took so long for Firefox to decide that this should be a rolled-in feature? As others have noted, Firefox director Mike Beltzner declared that the feature would need to take a backseat to keeping the browser on schedule.
Pressure from this being a near-universal feature has no doubt accelerated its importance, although Mozilla plans to put its own spin on what it can do. In addition to turning off the page cache and the browsing history recorder, there will be no autofill for passwords and new passwords used will not be saved. Also, all cookies acquired during the session will be discarded, as will downloads in the Download Manager. Essentially, pages visited will be stored in the memory, not on the hard disk--although there's no word on if or how this will affect performance.
Another aspect of the current unnamed feature will save all tabs and close the session, re-opening a new blank browser window. When the private session is finally turned off, the older session will re-open. One difference from Microsoft's InPrivate will be that there won't be any neon advertising that private mode has been activated, according to Mike Connor, the lead developer on Firefox. The fact that you are using a privacy mode will remain private.