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I have a late 2013 15" Macbook Pro Retina (the newest model as of the time of this question). I've seen numerous blog posts that show this computer powering 3 external displays, plus the built in retina display, but I can't make it work. I have a 22" ASUS connected by mini display to VGA adapter, a 30" Hannspree connected by mini display to HDMI adapter, and a 22" LG connected to the built-in HDMI. I can get every combination of 2 monitors working plus the built-in, but I can't get all 3 external on at the same time. I've tried with the built-in open and closed. I've also tried using 2 mini display to VGA adapters. According to a CNET article, this should work!