I was pointed to this add-on in the Firefox Builds forum when I had first inquired why my App Tabs were loading in Firefox 9 Beta upon start-up even though I had Don’t load tabs until selected checked. I had thought that my profile was broken (which it was, but unrelated to this normal behavior). This after being told App Tabs are for web applications not normal pages.I know I was not using them for the intended purpose, but I liked how the app tab took up 85% less space on my tab bar. Tab Utilities allows me to ‘Faviconize’ a regular tab, which will not be loaded until start-up.

Now, a word of warning before you go and install this add-on, it is very feature rich and the UI can be a bit over-whelming (see screenshots at the bottom of this post). While there is a ‘lite’ version it does have the ability to Faviconize tabs. So once the add-on is installed there a couple minor settings you need to change:

• Add ‘Faviconize Tab’ context menu option:
• From Firefox go to Tools > Tab Utilities Options….
• Click on Appearance then select the Menu tab
• In the first column (Tab Context Menu) check Faviconize Tab(it is in the second set of options)
• Force new tabs opened via a link to open to the far right (with App Tabs, a new tab would open to the right of the last app tab):
• From Firefox go to Tools > Tab Utilities Options….
• (If needed) Click on Tabs and Tab Opening
• In the 2nd section below, Open new tabs next to current tab which are from: select None.
  

Now that these options have been changed, it is time to Faviconize your tabs. First, be sure the tabs are NOT currently pinned (right-click on tab and select Unpin Tab). Right-click on the tab and select Faviconize Tab (or CTRL+ALT+I). Note: Unlike App Tabs, Faviconized Tabs are not grouped together on the left by default, the tab will be Faviconized in its current position on the tab bar. You can move the Faviconized tab to where you want. Warning: You can mix and match app tabs/Faviconized tabs (I have Brief and Hotmail as app tabs since I do want those loading on start-up, but also want them Faviconized) and moving a Faviconized tab to the left of an app tab will make it an app tab resulting in the tab being loaded upon start-up in Firefox 9.

Another nice feature is you can setup your bookmarks to be loaded as Faviconized as well.

Tab Utilities works with Firefox 3.6 and above and is about 97 KB.