1. Project settings
To avoid getting rendering issues and to ensure your material is exported in the right format, always remember to adjust the project settings to fit the media you want to render. 

• To change the project settings, go to "File" (or "Project") > "Properties" and select the template which is most appropriate for your material.
• If you aren't sure which template to choose, click the "Match Media Settings" button (the one with the folder icon in the upper right-hand corner of the "Properties" dialog).
• Click "Open". The software will then automatically select the appropriate template for you.
• Finally, click "OK".

2. Export format
For online videos, we recommend using the "Sony AVC / AAC (* .mp4)" format.
This format provides multiple SD and HD templates with a range of different settings and aspect ratios.

YouTube supports the following upload formats: 
https://support.google.com/youtube/troubleshooter/2888402?hl=en&rd=1

Using these settings will ensure that YouTube can play your video in maximum HD quality. To get the best possible quality for each video, try using different formats until you find the best one.

3. Pixel Aspect Ratio
Regardless of which format you choose, you should always set the "Pixel Aspect Ratio" to 1. This setting can be found by clicking the "Custom" button in the "Render as" window.
When you use this setting, the program renders your video with square pixels, which improves the picture quality.