Swipe

A swipe and a drag are the same physical movement judged by different criteria. A drag is aimed: the object follows the finger and the release point decides the outcome, so slowness costs nothing and precision is the point. A swipe is thrown: what matters is the direction and the speed, and the finger usually lets go over nothing in particular. That is why a swipeable surface has to accept two ways of committing. Past a distance threshold (a quarter of the page is a common figure), or under it but fast enough that the velocity carries it, the surface completes the move; short and slow, it springs back to where it started.

The direction is the vocabulary. Horizontal swipes page between siblings, which is how carousels, photo viewers, and tab strips move, and the platforms reserve the screen edges for going back. Vertical swipes scroll, and a vertical swipe near the bottom edge is the system’s own. Everything left over is a shortcut on a row: revealing the actions parked behind an inbox item is a swipe with a target, which is the case where the two families meet. Whatever the direction, the surface should follow the finger while the gesture is live, because a swipe that only reveals its result on release is indistinguishable from a control that did not notice.

Swipes are invisible. Nothing on screen says a surface can be thrown, so a swipe can be an accelerator and never the only route: page indicators earn their place partly by saying there is somewhere to go, and a peek of the next page at the screen edge does the same job better. The gesture also collides with things it does not own. A horizontal swipe inside a vertical scroller needs a decision about which axis wins (the web spells this touch-action, and taking the whole gesture with touch-action: none means taking responsibility for scrolling too), and a swipe that starts within a few millimetres of the screen edge probably belongs to the operating system rather than to your page.

The word gets stretched to the mouse, where it is really a drag: a pointer does not flick, and a trackpad’s two-finger swipe arrives as a scroll or a history gesture rather than as anything a page can listen for. If a behaviour matters on the desktop, put arrows or a keyboard route beside it rather than hoping the gesture translates.