Force touch

Force touch is a press with a third dimension. The contact reports how hard it is pushing, and the interface watches that reading for a line being crossed: past the first threshold a preview lifts, past the second the preview commits and becomes the thing itself. Apple shipped the idea twice under two names, as Force Touch on the 2015 trackpad and as 3D Touch on the iPhone 6s, and gave the two thresholds names that stuck: peek and pop. The specimen above performs the press rather than picking its outcome: the finger holds the row, the reported pressure climbs while the gauge reads it, and each mark fires as it is crossed. A pointer with no force sensor makes the same gesture by holding, buying depth with time, which is the very trade Haptic Touch later made official.

The contrast with pressure sensitivity is worth stating flatly, since the two read the same sensor. Pressure sensitivity maps a continuous force onto a continuous property, so every value along the axis means something and the stroke keeps getting wider the harder the pen is pushed. Force touch throws almost all of that away: it watches the axis for two lines and produces a discrete command, which makes it a button with deep travel rather than a dial. That is also why it leans on haptic feedback harder than any other gesture. Depth is invisible, the finger never moves, and without a tick at each threshold a reader cannot tell a press that fired from a press that did not.

The web never got a standard for it. WebKit exposed force clicks through non-standard events (webkitmouseforcewillbegin, webkitmouseforcedown and their siblings) plus a webkitForce reading and two constants naming the thresholds, and nothing else ever implemented them. What is standard is pressure on a pointer event, which most hardware reports as a flat 0.5 for the whole time a button is held, so a threshold built on the web is mostly a number the interface cannot trust. Apple retired the hardware too: the iPhone XR and everything after it replaced 3D Touch with Haptic Touch, which is a long press wearing the same clothes, and the peek it lifts is now bought with time instead of force.

The design lesson survived the hardware. Nothing on a screen announces that a target can be pressed harder, so force touch was only ever an accelerator, and everything it reached had to have a visible route as well: a row of actions, an overflow menu, a plain tap that opens the same record. It also has to be forgiving in both directions, because a firm tapper fires peeks nobody asked for and a light one never reaches the first mark at all. The preview a peek lifts is a quick view by another name, which is the honest way to read the whole pattern: a good idea about previewing, delivered through an input almost nobody could discover.