Mod tile is a system to serve raster tiles for example to use within a slippy map. It provides a dynamic combination of efficient caching and on the fly rendering. Due to its dynamic rendering, only a small fraction of overall tiles need to be kept on disk, reducing the resources required. At the same time, its caching strategy allows for a high performance serving and can support several thousand requests per second.

Mod_tile was originally written for serving the tiles of the main OSM map (Mapnik layer), but since is being used on a variety of different servers providing maps on top of OpenStreetMap data.