The actual value of a CSS property is the used value of that property after any necessary approximations have been applied. For example, a user agent that can only render borders with a whole-number pixel width may round the thickness of the border to the nearest integer.

Calculating a property's actual value

The user agent performs four steps to calculate a property's actual (final) value:

  1. First, the specified value is determined based on the result of cascading, inheritance, or using the initial value.
  2. Next, the computed value is calculated according to the specification (for example, a span with position: absolute will have its computed display changed to block).
  3. Then, layout is calculated, resulting in the used value.
  4. Finally, the used value is transformed according to the limitations of the local environment, resulting in the actual value.

Specifications

Specification Status Comment
CSS Level 2 (Revision 1)
The definition of 'actual value' in that specification.
Recommendation Initial definition.

See also

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Last updated by: mfluehr,