Why do different browsers embed background url differently (as data url vs. http)

I'm currently testing with cypress and verifying whether the background image is uploaded correctly. On my local system I'm using Chrome and in the CSS it says:

url("data:image/png;base64....

But Jenkins is using Electron and there it says:

url("https://testing....

I'm comparing the URLs with each other and of course it fails on Jenkins.

Why is the URL different for different browsers? Is there a way to set a specific type of the image resource (data url or http)? Is there another way to verify whether the image is uploaded correctly?