Skip to content


Switch branches/tags


Join the chat at Dependency Status Node.js CI

Very lite but extendable mapping framework to create Mapnik ready maps with OpenStreetMap data (and more).

For now, only Carto based projects are supported (with .mml or .yml config), but in the future we hope to plug in MapCSS too.


Only the core needs:

  • project loading
  • local configuration management
  • tiles server for live feedback when coding
  • exports to common formats (Mapnik XML, PNG…)
  • hooks everywhere to make easy to extend it with plugins



Install or Update

Note: Node.js versions are moving very fast, and kosmtik or its dependencies are hardly totally up to date with latest release. Ideally, you should run the LTS version of Node.js. You can use a Node.js version manager (like NVM) to help.

npm -g install kosmtik

This might need root/Administrator rights. If you cannot install globally you can also install locally with

npm install kosmtik

This will create a node_modules/kosmtik folder. You then have to replace all occurences of kosmtik below with node node_modules/kosmtik/index.js.


To get command line help, run:

kosmtik -h

To run a Carto project (or .yml, .yaml):

kosmtik serve <path/to/your/project.mml>

Then open your browser at

You may also want to install plugins. To see the list of available ones, type:

npm search kosmtik

Configuration file

By default Kosmtik places a configuration file into $HOMEDIR/.config/kosmtik.yml where $HOMEDIR is your home directory. You can change that by setting the environment variable KOSMTIK_CONFIGPATH to the appropriate file.

In the configuration file Kosmtik stores information about installed plugins and you can change certain settings that should be persistent between runs.

Configurable settings are:

  • autoReload (true/false)
  • backendPolling (true/false)
  • cacheVectorTiles (true/false)
  • dataInspectorLayers (object with layer names and true/false)
  • exportFormats (array of strings)
  • showCrosshairs (true/false)

Local config

Because you often need to change the project config to match your local env, for example to adapt the database connection credentials, kosmtik comes with an internal plugin to manage that. You have two options: with a json file named localconfig.json, or with a js module name localconfig.js.

Place your localconfig.js or localconfig.json file in the same directory as your carto project (or .yml, .yaml).

In both cases, the behaviour is the same, you create some rules to target the configuration and changes the values. Those rules are started by the keyword where, and you define which changes to apply using then keyword. You can also filter the targeted objects by using the if clause. See the examples below to get it working right now.

Example of a json file

        "where": "center",
        "then": [-122.25, 49.25, 10]
        "where": "Layer",
        "if": {
            "Datasource.type": "postgis"
        "then": {
            "Datasource.dbname": "vancouver",
            "Datasource.password": "",
            "Datasource.user": "ybon",
            "": ""
        "where": "Layer",
        "if": {
            "id": "hillshade"
        "then": {
            "Datasource.file": "/home/ybon/Code/maps/hdm/DEM/data/hillshade.vrt"

Example of a js module

exports.LocalConfig = function (localizer, project) {
    localizer.where('center').then([29.9377, -3.4216, 9]);
    localizer.where('Layer').if({'Datasource.type': 'postgis'}).then({
        "Datasource.dbname": "burundi",
        "Datasource.password": "",
        "Datasource.user": "ybon",
        "": ""
    // You can also do it in pure JS
    project.mml.bounds = [1, 2, 3, 4];

Custom renderers

By default Kosmtik uses Carto to render the style. Via plugins it is possible to use other renderers or Carto implementations. You can switch the renderer installing the appropriate plugin and by passing the command line option --renderer NAME. NAME refers to the renderer name (e.g. carto for the default renderer or magnacarto for the Magnacarto renderer).

Known plugins

Run npm search kosmtik to get an up to date list.