Did you know that Facebook quietly changed the pixel dimensions for cover photos of Facebook pages a few months back? I didn’t realize it at the time, though I did notice a small change in how things displayed. For reference, the old size was 851 pixels wide by 315 pixels tall.
There are now two sizes in use. On mobile devices (the majority of traffic) the size is 828 pixels wide by 465 pixels tall. Desktop viewers will see the same image, but the top and bottom are cropped so you see 828 pixels wide by 315 pixels tall. Below is a PNG version of the template showing the two sizes. Dark blue is the mobile version and the brighter blue is the desktop version.
Because of the areas at top and bottom, you could include content that only your mobile visitors will see. Or you can leave that as “white” space that is just cropped out on desktop. I’ve created a CorelDRAW X5 file you can use as a template. If that format doesn’t work for you, you can also use the PNG file displayed above in your software of choice.
Note that this change only applies to the cover photos on pages and not on personal profiles. Of course I wouldn’t be shocked if the sizes for personal profiles are also change at sometime in the near future.