Interaction design through proximity

Time-of-flight sensors allow for computers and participating objects to have awareness of their relative positions to one another in space. This allows for very natural interactions between devices: a laptop and an external display can know which direction to extend a desktop to, for example.

Apple’s Human Interface Guidelines have the following guidelines:

  • Consider a task from the perspective of the physical world to find inspiration for a nearby interaction. For example, although people can easily use your app’s UI to transfer a song from their iPhone to their HomePod mini, initiating the transfer by bringing the devices close together makes the task feel rooted in the physical world. Discovering the physical actions that inform the concept of a task can help you create an engaging experience that makes performing it feel easy and natural.

  • Use distance, direction, and context to inform an interaction. Although your app may get information from a variety of sources, prioritizing nearby, contextually relevant information can help you deliver experiences that feel organic. For example, if people want to share content with a friend in a crowded room, the iOS share sheet can suggest a likely recipient by using on-device knowledge about the person’s most frequent and recent contacts. Combining this knowledge with information from nearby devices that include the U1 chip can let the share sheet improve the experience by suggesting the closest contact the person is facing.

  • Consider how changes in physical distance can guide a nearby interaction. In the physical world, people generally expect their perception of an object to sharpen as they get closer to it. A nearby interaction can mirror this experience by providing feedback that changes with the proximity of an object. For example, when people use iPhone to find an AirTag, the display transitions from a directional arrow to a pulsing circle as they get closer.

  • Provide continuous feedback. Continuous feedback reflects the dynamism of the physical world and strengthens the connection between a nearby interaction and the task people are performing. For example, when looking for a lost item in Find My, people get continuous updates that communicate the item’s direction and proximity. Keep people engaged by providing uninterrupted feedback that responds to their movements.

  • Consider using multiple feedback types to create a holistic experience. Fluidly transitioning among visual, audible, and haptic feedback can help a nearby interaction’s task feel more engaging and real. Using more than one type of feedback also lets you vary the experience to coordinate with both the task and the current context. For example, while people are interacting with the device screen, visual feedback makes sense; while people are interacting with their environment, audible and haptic feedback complement their shift in focus.

  • Avoid using a nearby interaction as the only way to perform a task. You can’t assume that everyone can experience a nearby interaction, so it’s essential to provide alternative ways to get things done in your app.

Apple’s implementation uses a framework with appropriate sandboxing to call app functionality when certain proximity conditions are met.