CSS position sticky not working — common causes and fixes

position: sticky has no effect. The element scrolls normally instead of sticking. No errors — it just doesn't work.

Requirements: (1) Must have a threshold: top: 0. Without it, sticky has nothing to stick to. (2) Parent must not have overflow: hidden/auto/scroll — sticky breaks inside overflow containers. (3) Sticky element sticks within its parent — if parent is short, element scrolls away. (4) Check ancestors for any overflow property. (5) Flex/grid children may need align-self: start.

Sticky positioning is relative to the scroll container AND constrained by the parent element's box. It sticks until the parent's bottom edge reaches it.