How your video will display
The standard aspect ratio for YouTube on a computer is 16:9. If your video has a different aspect ratio, the player will automatically change to the ideal size to match your video and the viewer’s device.
Recommended resolution & aspect ratios
For the default 16:9 aspect ratio, encode at these resolutions:
How to Video Aspect Ratio?
Add a video file, Upload a clip from your computer
Choose output options (optional) Output Options
Download the edited video
Watch the video right in your browser. Now, when you are 100% satisfied with what you have done, click "Download".