Hub and spoke

Hub and spoke is the shape a launcher has. One screen holds the whole menu, choosing a tile takes over the screen, and the only route out is back to the tile screen. Drawn as a graph it is a star: every edge touches the centre, and there is not one edge between any two tasks. The original iPhone home screen was the canonical example, along with almost every smartwatch, television, and kiosk since, because all three share the same constraint of a screen too small or too far away to carry persistent chrome.

What the shape buys is a home that is genuinely a home. There is exactly one place to return to, the tasks do not have to agree about anything, and each spoke gets the entire screen, which matters most on the devices where the screen is the scarce thing. It is also the friendliest shape for an occasional user, since the whole product is legible from one picture, and it lets tasks be added or removed without renegotiating a navigation bar.

What it costs is lateral movement, and the cost is real rather than theoretical. The specimen above measures it: from the home screen four tasks are one tap away, and from inside a task exactly one destination is, which is home. A reader who wants to check the calendar while replying to a message has to leave the reply, go home, and come back the same way, and the more often they cross between two spokes the worse the shape reads. That is the diagnosis to make before adopting it: hub and spoke is right when the tasks are genuinely separate errands and wrong when they are steps in one job. Devices with persistent chrome usually keep the hub and add a shortcut layer beside it, a dock, a recents row, or a back gesture that remembers where the reader came from, which is a quiet admission that the pure star is too strict.

The neighbours are worth separating carefully. Persistent global navigation is the direct opposite: it keeps every top level destination on screen inside every destination, so a reader crosses from one sibling to another without passing through anything, where hub and spoke has no lateral edge at all. Drill-down navigation is about depth rather than breadth, a descent through a hierarchy where back is up one level, whereas a spoke is one level deep and back always lands in exactly the same place. Local navigation is what appears once a reader is inside a spoke and needs to move around within it, and list-detail is the shape that replaces hub and spoke the moment the screen is wide enough to show the menu and the task at the same time.