# Placekey Design

Each Placekey is divided into two parts: What and Where, written as βWhat@Whereβ. The What part encodes information about the place and its address, while the Where part situates that place on Earth. The What part of a Placekey is optional, and a What less Placekey like β@5vg-7qg-tvzβ refers to a region on the Earth while a What part plus a Where part specifies a particular place within a region on the Earth. β

The Where part of a Placekey encodes a hexagon of approximately 15,000 m2 on the surface of the Earth. These hexagons have an edge length of 66 m on average, and it can be helpful to think of them as roughly circles with a diameter of 132 m. The exact area and edge length of the hexagon varies by location. In particular, these hexagons are given by resolution 10 H3 indices.

The What part of a Placekey encodes an address (when it is just about an address) or an address and a POI (when a POI is present). Encodings that start with a zero β0β refer to addresses and those that start with a one β1β refer to a POI. In the future, there might be other types that start with a 2, 3, etc. What parts are only unique up to the Where part of a Placekey.

More details on the design of Placekey can be found here.

ποΈ You may notice some placekeys structured in a slightly different way like 227-223@5vg-82n-pgk. These are before a major update but still usable in matching and will remain consistent. Please think of these as usable strings.

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