What are the Default Values for `top`, `left`, `bottom`, and `right` when Using `position: absolute`?

Default Values for Position: Absolute

When using the position: absolute CSS property without specifying any values, it is important to understand the default values for the top, left, bottom, and right properties. Contrary to popular belief, these values are not set to 0 by default.

Instead, the default value for all these properties is "auto." This means that the element remains in its normal position in the layout, as if it were not positioned at all. This is known as the "static position."

The behavior of an element with all of its offset values set to "auto" is defined in the CSS specification. For the horizontal position, the constraint is:

'left' + 'margin-left' + 'border-left-width' + 'padding-left' + 'width' + 'padding-right' + 'border-right-width' + 'margin-right' + 'right' = width of containing block

If all three of 'left', 'width', and 'right' are "auto," the element's width is set to "shrink-to-fit," and the 'left' value is determined based on the static position.

Similarly, for the vertical position, the constraint is:

'top' + 'margin-top' + 'border-top-width' + 'padding-top' + 'height' + 'padding-bottom' + 'border-bottom-width' + 'margin-bottom' + 'bottom' = height of containing block

If all three of 'top', 'height', and 'bottom' are "auto," the element's top value is set to the static position, and its height is determined based on its content.

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