Show polygon data from GeoJSON on the map

In this tutorial, we will demonstrate the process of incorporating a GeoJSON polygon overlay onto the map. Through the following steps, you will learn how to seamlessly integrate this feature into your web mapping applications.

1. Copy the following code, paste it into your favorite text editor, and save it as a .html file.

2. Install the npm package.

3. Include the CSS file.

   If you have a bundler that can handle CSS, you can import the CSS or include it with a <link> in the head of the document via the CDN

4. Include the following code in your JavaScript file (Example: app.js).

5. Replace YOUR_MAPTILER_API_KEY_HERE with your actual MapTiler API key.

6. The next is up to you. You can center your map wherever you desire (modifying the starting position) and set an appropriate zoom level (modifying the starting zoom) to match your users’ needs. Additionally, you can change the map’s look (by updating the source URL); choose from a range of visually appealing map styles from our extensive MapTiler standard maps, or create your own to truly differentiate your application.

7. Add event handler for map load event. You will add code to create a GeoJSON source and a vector layer in this handler.

   
    map.on('load', async function() {
       
    });
    

8. Create GeoJSON source. The following snippet creates GeoJSON source hosted on MapTiler Cloud (check out the How to Upload GeoJSON to MapTiler Cloud tutorial). Publish the dataset and copy the link to the GeoJSON. Download the Rio de Janeiro sample data.

   
        map.on('load', async function() {
            const geojson = await maptilersdk.data.get('YOUR_MAPTILER_DATASET_ID_HERE');
            map.addSource('rio_cats', {
                type: 'geojson',
                data: geojson
            });
        });
    

9. Add the vector layer

   
        map.addLayer({
            'id': 'rio_cats',
            'type': 'fill',
            'source': 'rio_cats',
            'layout': {},
            'paint': {
                'fill-color': '#98b',
                'fill-opacity': 0.8
            }
        });
    

Learn more

Check out the tutorials on How to add a GeoJSON in MapLibre (video & code) to learn how to load a point GeoJSON and change the point icon.

Related examples

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Polygon layer (polygon helper)

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This example shows how to add a polygon layer to the map using the polygon layer helper.

GeoJSON multiGeometry layer

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This tutorial shows how to add a GeoJSON MultiGeometry overlay to the map.

Choropleth GeoJSON

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This tutorial shows how to add a styled GeoJSON overlay to the map, display a popup on click, and create a map legend.