Bing Maps quadkey decoder

A Bing Maps quadkey is a compact base-four address for one square in the global Web Mercator tile pyramid used by Bing Maps, Azure Maps, and many compatible tile caches. Instead of three separate integers for zoom, column, and row, a single string of digits zero through three encodes the full path from the root tile down to a leaf.

How a Bing Maps quadkey becomes tile X, Y, and zoom

The Microsoft Bing Maps Tile System builds a square pyramid in Web Mercator. At zoom one the world splits into four child quadrants labeled zero, one, two, and three; each deeper zoom appends another digit by subdividing the parent. Reading the string from left to right therefore walks from the coarsest bit to the finest bit of the tile indices.

Zoom equals the string length: a three-character key such as two one three is always zoom three, and a sixteen-character key is always zoom sixteen. To recover X and Y, initialize both coordinates to zero, then for each bit position from most significant to least significant apply a binary mask of one shifted left by the remaining depth. Digit zero leaves both bits clear, digit one sets the X bit, digit two sets the Y bit, and digit three sets both bits.

After every digit has been applied, X and Y are ordinary non-negative integers in the half-open range from zero through two to the zoom minus one, matching the familiar z slash x slash y scheme used by OpenStreetMap-style servers once you know the zoom. Classic documentation checks include the key two one three decoding to X equals three and Y equals five at zoom three, and the single digit one decoding to X equals one and Y equals zero at zoom one.

What you send and what you get back

Send one required string under the field quadkey. The value must be a non-empty sequence of the digits zero, one, two, and three only; spaces are trimmed at the edges, but internal whitespace and letters fail validation. Use the free browser form when you are inspecting a suspicious cache key from a Bing or Azure Maps URL and need the XYZ triple immediately.

Call the identical contract from scripts when you migrate a quadkey store to an XYZ tile CDN, generate answer keys for GIS coursework, or assert that a fixed landmark quadkey still maps to the same column and row after a library upgrade. Pair this decoder with a separate encoder or lat-lon-to-tile landing when your workflow needs the inverse direction rather than overloading a single form.

Where Bing quadkey decoding shows up in real work

Map platform engineers constantly receive Bing or Azure Maps tile URLs that embed a quadkey path segment and need the equivalent column and row for an XYZ cache, a debug overlay, or a comparison against OpenStreetMap tiles of the same pyramid cell. Backend services that historically stored only quadkeys for compact primary keys still need a trusted closed form to join against slippy-map shards, warm CDN regions, or export GeoJSON features keyed by z slash x slash y.

Curriculum authors teaching web mapping and GIS want students to see base-four quadrant labels produce integer indices without a silent clamp or floating-point projection step. Logistics and privacy pipelines that keep coarse pyramid keys can decode a batch of quadkeys into bounding tile indices for analytics while keeping the conversion pure and offline.

If you later need the inverse encode of X Y zoom into a quadkey, lat lon to slippy tile indices, or great-circle destination points, treat those as separate search intents and landings rather than overloading this Bing Maps quadkey decoder page.