Can I upload my own videos?
The Video Background app only works with YouTube and Vimeo videos.
YouTube and Vimeo provide the best streaming infrastructure in the world, so your background videos will work better and much smoother using any of those.
We don't support uploading your own videos to avoid performance issues since Shopify's platform lacks the capability to stream videos. When your own videos are uploaded to a web server, like Shopify’s servers, they are not streamed but downloaded, which has a huge impact on its performance.
In contrast, when a video is uploaded to YouTube and Vimeo, it will be streamed in a well-optimized way.
Uploading and managing videos on YouTube and Vimeo is a very easy task that can be done in a couple of minutes even using your mobile device.
Please refer How to upload video to YouTube? Or Uploading to Vimeo for future references.