Do black bars appear only to the sides?

Sorry for the noob question.

But, let's say i set height of layout to 480. If the device has different aspect ratio with display of height 1024, will black bars appear at top and bottom?

The black bars will appear when the project's dimensions doesn't match the screen's dimensions. The placement of the bars depends on your project's ratio in relation the screen's ratio.

A 16:9 project viewed on a 4:3 screen will have top/bottom black bars.

A 4:3 project viewed on a 16:9 screen will have left/right black bars.

Thanks Elios So a 16:9 viewed on 16:10,3:2,4:3 or 5:4 will only be cropped on the sides?

sansolo , since you are mentioning cropping, I assume that you don't use the letterbox scale option but instead the crop...?

If yes, then the actual pixel resolution of your window and layout size will play a role on how the game will be cropped. A 1280x720px game with a 1280x720px layout will have white space on the top/bottom of a 16:10 screen that has 1280x800 px resolution. If the layout is much bigger than the window size, then at the top/bottom of the screen it will be visible. The same thing will happen if the screen has a 1920x1200 px resolution. On a window=layout=1280x720 px there will be white space all around the layout if viewed on a screen that has higher resolution.

However, if you use the letterbox scale, then on all of the ratios that you mentioned, there will be black bars on the top/bottom. In fact, if we keep the order of the ratios in your post the bars will be incising in size as we get closer to the 5:4.