# TopoJSON

**TopoJSON** is an extension of GeoJSON that encodes topology. Rather than representing geometries discretely, geometries in TopoJSON files are stitched together from shared line segments called *arcs*. TopoJSON eliminates redundancy, offering much more compact representations of geometry than with GeoJSON; typical TopoJSON files are 80% smaller than their GeoJSON equivalents. In addition, TopoJSON facilitates applications that use topology, such as [topology-preserving shape simplification](http://bost.ocks.org/mike/simplify/), [automatic map coloring](http://bl.ocks.org/4188334), and [cartograms](http://prag.ma/code/d3-cartogram/).

Want to learn more? [See the wiki.](https://github.com/mbostock/topojson/wiki)