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Not Good For Mobile Web Page Testing Rated 3 out of 5 stars
While it does switch the User Agent, this addon is pretty much useless when testing Mobile webpages. It doesn't detect the size of the screen to switch the view between profile and landscape. Chrome is far superior with it's built in features to switch User Agents. I prefer Firebug in Firefox over Chrome, but testing mobile sites on Firefox is still way behind the game.