Does Swiper's parent automatically block touch when a nested child Swiper is active?

Direct answer

Yes. When the parent Swiper is initialized with nested: true and the child Swiper is initialized with touch moves enabled, the parent ignores pointer events while a drag is active over the child. The child consumes the swipe and the parent does not change slides. This suppression is not automatic when nested is omitted or false; in that configuration the parent can still receive touchstart and slide while the child is being dragged.

Likely explanation versus verified behavior

Likely explanation: Swiper's nested mode handles pointers at the container level and suppresses the parent's own touch tracking when a drag originates inside an active child instance. The parent's allowTouchMove does not re-enable parent touches during that child drag; nested: true takes precedence. Setting allowTouchMove: false, or a function returning false, blocks the parent independently of the child state.

Behavior to verify:

• Swiper 8.x and 9.x use the same nested touch-propagation mechanism; no functional difference is expected between those versions.
• The child must keep allowTouchMove enabled, which is the default, for nested suppression to engage.
• If the child is destroyed, not yet initialized, or styled with pointer-events: none, the parent may still receive touches.

Steps for this case

1. Initialize the parent with nested: true.
2. Initialize the child inside a parent slide with allowTouchMove: true, which is the default.
3. Add a temporary touchstart listener on the parent wrapper and confirm it does not fire while dragging the child.
4. To block the parent regardless of the child, set parent allowTouchMove: false or a function returning false.

const parent = new Swiper('.parent', {
  nested: true,
  allowTouchMove: true,
});

const child = new Swiper('.child', {
  // allowTouchMove defaults to true
});

Verification

Drag the child and confirm the parent slide index does not change. Then set parent nested: false and repeat; the parent should now slide while the child is dragged. Run the same steps in Swiper 8.x and 9.x to confirm identical outcomes.

Are you using lazy-loaded or virtual slides inside the child? Delayed child rendering can temporarily break nested touch blocking until the child is ready.