The value of this property is overridden by any declaration of the background or background-position shorthand properties applied to the element after it.

/* Keyword values */
background-position-y: top;
background-position-y: center;
background-position-y: bottom;

/* <percentage> values */
background-position-y: 25%;

/* <length> values */
background-position-y: 0px;
background-position-y: 1cm;
background-position-y: 8em;

/* Side-relative values */
background-position-y: bottom 3px;
background-position-y: bottom 10%;

/* Multiple values */
background-position-y: 0px, center;

/* Global values */
background-position-y: inherit;
background-position-y: initial;
background-position-y: revert;
background-position-y: revert-layer;
background-position-y: unset;

The background-position-y property is specified as one or more values, separated by commas.

top

Aligns the top edge of the background image with the top edge of the background position layer.

center

Aligns the vertical center of the background image with the vertical center of the background position layer.

bottom

Aligns the bottom edge of the background image with the bottom edge of the background position layer.

<length>

The offset of the given background image's horizontal edge from the corresponding background position layer's top horizontal edge. (Some browsers allow assigning the bottom edge for offset).

<percentage>

The offset of the given background image's vertical position relative to the container. A value of 0% means that the top edge of the background image is aligned with the top edge of the container, and a value of 100% means that the bottom edge of the background image is aligned with the bottom edge of the container, thus a value of 50% vertically centers the background image.

background-position-y = 
  [ center | [ [ top | bottom | y-start | y-end ]? <length-percentage>? ]! ]#  

<length-percentage> = 
  <length>      |
  <percentage>  

The following example shows a simple background image implementation, with background-position-x and background-position-y used to define the image's horizontal and vertical positions separately.

HTML

<div></div>

CSS

div {
  width: 300px;
  height: 300px;
  background-color: skyblue;
  background-image: url(https://mdn.dev/archives/media/attachments/2020/07/29/17350/3b4892b7e820122ac6dd7678891d4507/firefox.png);
  background-repeat: no-repeat;
  background-position-x: center;
  background-position-y: bottom 10px;
}

Result

• background-position
• background-position-x
• background-position-inline
• background-position-block
• Using multiple backgrounds