In order to have wide-fullscreen videos on YouTube (without any black borders), the resolution for your videos should have a 16:9 aspect ratio.
For Sony Vegas, check the “event pan/crop” option to change the aspect ratio.
The event pan/crop tool from Sony Vegas can be accessed by clicking on that square.
Here are some 16:9 (wide-screen) resolutions (that you should use)
3840×2160 2560×1440 1920×1080 1600×900 1280×720 854×480 640×360 426×240.
If you record videos by using a resolution that is not 16:9, you will get black borders on YouTube.
In a video game or from where you want to record your screen, you should aim for the resolutions that are marked there by being “wide”.
If your monitor doesn’t have a 16:9 wide aspect ratio, you can set the video game to run “windowed” and pick a 16:9 resolution like 1280×720.
If you set the resolution to 1280×720 but you still play the game in fullscreen mode, your video will not have a 16:9 aspect ratio and it will have black borders on YouTube.
Render your videos in a 16:9 aspect ratio, using any of the resolutions mentioned here.
Thumbnail size for YouTube
The thumbnails can have any size but the size should have an 16:9 aspect ratio.
How to make an image that has 16:9 aspect ratio? It’s very easy. From Adobe Photoshop, click on the “crop” tool and from the upper fields, type 16 in for width and 9 in for height.
And just crop your image. The thumbnail should have the correct size.
An example of a 16:9 wide video on YouTube.
If you have any questions, please leave in the comments.