World-space modifiers are carried with the object to which they're assigned, but use world space rather than object space for their effects. World-space modifiers are convenient for modifying a single object or selection set.
World-space modifiers are applied like a standard object-space modifier. You can access the world-space modifier from the Modifier List in the Modify panel or from the Modifiers menu. A world-space modifier is indicated by either an asterisk or the letters “WSM” next to its name wherever it's found to identify it as such, and distinguish it from the comparable object-space modifier, if one exists.
When you assign a world-space modifier to an object, it appears at the top of the modifier stack listed as a binding.
For a list of world-space modifiers, see List of Available Modifiers.