Simplify
Export
Shapefile
GeoJSON
TopoJSON

Unfortunately, mapshaper can't run in this web browser

For best results, try Google Chrome or Mozilla Firefox.

Please note

This version of Mapshaper is maintained for readers of Implications of Weighting Metrics for Line Generalisation with Visvalingam’s Algorithm (Visvalingam and Whelan, 2014). The latest version (available here) uses a different function for weighted Visvalingam simplification than the function discussed in the paper.

There are several options for those who would like to help improve Mapshaper. You can:

  • request a feature or report a bug using the issue tracker
  • view the latest version of the source code on Mapshaper's project page
  • view this version (0.2.0) of the source code.
  • send feedback to Mapshaper's creator (Matthew Bloch) at masiyou@gmail.com

Edit a file

Drag a Shapefile .shp, GeoJSON or TopoJSON file onto this window, or select a file from a local folder.

Simplification method

?
Simplified lines remain within a given distance of original lines. Good for thinning dense points but tends to form spikes at high simplification.
?
Lines are simplified by iteratively removing the point that forms the least-area triangle with two adjacent points.
?
Points located at the vertex of more acute angles are preferentially removed, for a smoother appearance.

Other options

?
Remove line intersections. Works by rolling back simplification along intersecting segments.
?
Automatically fix minor topology errors by snapping together points that are almost identical. Doesn't apply to TopoJSON files.
?
Prevent small polygons from disappearing at high simplification. Protects the largest ring of multi- ring features.
coordinate precision
?
Round coordinates by a specified precision. Reduces the size of GeoJSON files but can cause intersections and collapsed shapes. Uses same units as the source file, e.g. decimal degrees for most unprojected files.
0 line intersections
Repair