Mapshaper
Introduction
Mapshaper is software for editing Shapefile, GeoJSON, TopoJSON, CSV and several other data formats, written in JavaScript.
Mapshaper supports essential map making tasks like simplifying shapes, editing attribute data, clipping, erasing, dissolving, filtering and more.
See the documentation for guides, examples and a complete command reference.
If you're using an AI assistant or another tool that can read documentation, point it at mapshaper.org/llms.txt — an llms.txt index of every docs page in machine-readable form. Each page is also available as Markdown by appending .md to its URL (for example, mapshaper.org/docs/essentials/command-line.html.md). The full corpus in a single file is at mapshaper.org/llms-full.txt.
To suggest improvements, add an issue.
Command line tools
Mapshaper includes several command line programs, which can be run under Mac OS X, Linux and Windows.
mapshaper Runs mapshaper commands.mapshaper-xl Works the same as mapshaper, but runs with more RAM to support larger files.mapshaper-gui Runs the mapshaper Web interface locally.
The docs include an introduction to using the command line tool that includes many simple examples.
For a detailed reference, see the Command Reference.
Interactive web interface
Visit the public website at www.mapshaper.org or use the web UI locally via the mapshaper-gui script.
All processing is done in the browser, so your data stays private, even when using the public website.
The web UI works in recent desktop versions of Chrome, Firefox, Safari and Internet Explorer. Safari before v10.1 and IE before v10 are not supported.
User-contributed resources
rmapshaper is an R package written by Andy Teucher that gives R users access to many of mapshaper's editing commands.
Here are resources for using mapshaper with Docker, provided by Christian Weiss.
You can find a number of mapshaper tutorials online, including a two part guide to command line cartography by Dylan Moriarty and this introduction by Jack Dougherty.
Large file support
Web interface
Firefox is able to load Shapefiles and GeoJSON files larger than 1GB. Chrome has improved in recent versions, but is still prone to out-of-memory errors when importing files larger than several hundred megabytes.
Command line interface
There are hard limits for reading and writing most file types. The maximum output size of a single file of any type is 2GB. Some file types (GeoJSON, CSV, .shp, .dbf) are read incrementally, so much larger files can be imported.
When working with very large files, mapshaper may become unresponsive or crash with the message "JavaScript heap out of memory."
You can use mapshaper-xl as a replacement for the standard mapshaper program to allocate more heap memory (8GB by default). You can allocate even more memory like this: mapshaper-xl 20gb [commands].
Another option is to run Node directly with the --max-old-space-size option. The following example (Mac or Linux) allocates 16GB of heap memory:
$ node --max-old-space-size=16000 `which mapshaper` <mapshaper commands>
Installation
Mapshaper requires Node.js.
With Node installed, you can install the latest release version of mapshaper using npm. Install with the "-g" flag to make the executable scripts available systemwide.
npm install -g mapshaper
To install and run the latest development code from github:
git clone [email protected]:mbloch/mapshaper.git
cd mapshaper
npm install # install dependencies
npm run build # bundle source code files
npm link # (optional) add global symlinks so scripts are available systemwide
Using mapshaper with Bun
Mapshaper's command line tools can be run with Bun as an alternative to Node.js. The simplest option is to use bunx, like this:
bunx mapshaper [commands]
Building and testing
From the project directory, run npm run build to build both the cli and web UI modules.
Run npm test to run mapshaper's tests.
Supporting mapshaper
Mapshaper is free and open source. If it's useful to you or your organization, please consider supporting its continued development:
- Ko-fi — one-time or recurring contributions, no account required.
- GitHub Sponsors — recurring sponsorship.
You can also help by reporting bugs or telling me what you'd like to see improved.
License
This software is licensed under MPL 2.0.
According to Mozilla's FAQ, "The MPL's ‘file-level’ copyleft is designed to encourage contributors to share modifications they make to your code, while still allowing them to combine your code with code under other licenses (open or proprietary) with minimal restrictions."
Acknowledgements
My colleagues at The New York Times, for countless suggestions, bug reports and general helpfulness.
Mark Harrower, for collaborating on the original "MapShaper" program at the University of Wisconsin–Madison.
Mapbox, for donating basemap services to mapshaper.org.
