Interactive test on 'background-attachment': 'local' versus 'scroll' versus 'fixed' values

VeryLongUnbreakableWordToTriggerHorizontalScrollbar fixed
The background is fixed with regard to the viewport. In paged media where there is no viewport, a fixed background is fixed with respect to the page box and therefore replicated on every page. Note that there is only one viewport per view. Even if an element has a scrolling mechanism (see the overflow property [CSS2]), a fixed background doesn't move with the element.

local
The background is fixed with regard to the element's contents: if the element has a scrolling mechanism, the background scrolls with the element's contents, and the background painting area and background positioning area are relative to the scrollable area of the element rather than to the border framing them. Because the scrollable area does not include the border area, for scrollable elements the border-box value of background-clip may be treated the same as padding-box.

scroll
The background is fixed with regard to the element itself and does not scroll with its contents. (It is effectively attached to the element's border.)

Even if the image is fixed, it is still only visible when it is in the background painting area of the element or otherwise unclipped. (See "The backgrounds of special elements" for the cases when background images are not clipped.) Thus, unless the image is tiled, it may be invisible.