The background-image CSS property sets one or more background images for an element.
The background-size CSS property specifies the size of the background images.
Background-image isn t supposed to be animatable in the first place;on the other hand background-size can be animated but it s very clear from your css that you don t want to transition background-size
Background-size cover fade transition without size transition
However for some reason ulkit is making a background-size larger than my background-image
Uikit parallax: why background-size is being altered?