MBTiles
MBTiles is a format for storing a tileset in one file. Instead of millions of small files in nested folders, the tiles live as rows in a SQLite database, which makes a tileset something you can copy, move, or back up like any other file.
This matters at scale. A planet-wide tileset contains hundreds of millions of tiles, and most filesystems handle one large file far better than that many small ones.
What is inside
The database holds two things that matter:
- A
tilestable with a row per tile, keyed by zoom level, column, and row, with the tile itself stored as a blob. - A
metadatatable with the tileset name, format, bounds, minzoom, and maxzoom. For vector tilesets it also carries a JSON description of the layers and their fields.
The blobs can be raster tiles or compressed vector tiles, so the same container works for both.
One detail catches people out: MBTiles numbers rows from the bottom, following the TMS convention, while most web maps number them from the top. Tile servers handle the flip for you, but it explains why a map can come out upside down when tiles are read straight from the file.
Serving MBTiles
You do not extract the file to serve it. A tile server reads the database directly and answers tile requests from it.