You can specify whether a compound path is a nonzero winding path or an even‑odd path.

Nonzero winding fill rule

Uses mathematical equations to determine if a point is outside or inside a shape. Illustrator uses the nonzero winding rule as the default rule.

Even-odd fill rule

Uses mathematical equations to determine if a point is outside or inside a shape. This rule is the more predictable rule because every other region within an even‑odd compound path is a hole, regardless of path direction. Some applications, such as Adobe Photoshop, use the even‑odd rule by default, so compound paths imported from these applications will use the even‑odd rule.

Self-intersecting paths are paths that intersect themselves. You can choose to make these paths either nonzero winding or even‑odd, depending on how you want them to look.

Self-intersecting path with Use Non‑Zero Winding Fill Rule (left) compared with Use Even‑Odd Fill Rule (right)

When you create a nonzero winding compound path, you can specify whether overlapping paths appear with holes or are filled by clicking a Reverse Path Direction button in the Attributes panel.

Fill rules

A.

Four circular paths

B.

Circular paths selected, converted into compound path

C.

Reverse Path Direction applied to innermost path