Marker Clustering

Overview

This tutorial shows you how to use marker clusters to display a large number of markers on a map. You can use the @googlemaps/markerclusterer library in combination with the Maps JavaScript API to combine markers of close proximity into clusters, and simplify the display of markers on the map.

To see how marker clustering works, view the map below.

The number on a cluster indicates how many markers it contains. Notice that as you zoom into any of the cluster locations, the number on the cluster decreases, and you begin to see the individual markers on the map. Zooming out of the map consolidates the markers into clusters again.

The sample below shows the entire code you need to create this map.

TypeScript

function initMap(): void {
  const map = new google.maps.Map(
    document.getElementById("map") as HTMLElement,
    {
      zoom: 3,
      center: { lat: -28.024, lng: 140.887 },
    }
  );

  const infoWindow = new google.maps.InfoWindow({
    content: "",
    disableAutoPan: true,
  });

  // Create an array of alphabetical characters used to label the markers.
  const labels = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";

  // Add some markers to the map.
  const markers = locations.map((position, i) => {
    const label = labels[i % labels.length];
    const marker = new google.maps.Marker({
      position,
      label,
    });

    // markers can only be keyboard focusable when they have click listeners
    // open info window when marker is clicked
    marker.addListener("click", () => {
      infoWindow.setContent(label);
      infoWindow.open(map, marker);
    });

    return marker;
  });

  // Add a marker clusterer to manage the markers.
  new MarkerClusterer({ markers, map });
}

const locations = [
  { lat: -31.56391, lng: 147.154312 },
  { lat: -33.718234, lng: 150.363181 },
  { lat: -33.727111, lng: 150.371124 },
  { lat: -33.848588, lng: 151.209834 },
  { lat: -33.851702, lng: 151.216968 },
  { lat: -34.671264, lng: 150.863657 },
  { lat: -35.304724, lng: 148.662905 },
  { lat: -36.817685, lng: 175.699196 },
  { lat: -36.828611, lng: 175.790222 },
  { lat: -37.75, lng: 145.116667 },
  { lat: -37.759859, lng: 145.128708 },
  { lat: -37.765015, lng: 145.133858 },
  { lat: -37.770104, lng: 145.143299 },
  { lat: -37.7737, lng: 145.145187 },
  { lat: -37.774785, lng: 145.137978 },
  { lat: -37.819616, lng: 144.968119 },
  { lat: -38.330766, lng: 144.695692 },
  { lat: -39.927193, lng: 175.053218 },
  { lat: -41.330162, lng: 174.865694 },
  { lat: -42.734358, lng: 147.439506 },
  { lat: -42.734358, lng: 147.501315 },
  { lat: -42.735258, lng: 147.438 },
  { lat: -43.999792, lng: 170.463352 },
];

JavaScript

import { MarkerClusterer } from "@googlemaps/markerclusterer";

function initMap() {
  const map = new google.maps.Map(document.getElementById("map"), {
    zoom: 3,
    center: { lat: -28.024, lng: 140.887 },
  });
  const infoWindow = new google.maps.InfoWindow({
    content: "",
    disableAutoPan: true,
  });
  // Create an array of alphabetical characters used to label the markers.
  const labels = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  // Add some markers to the map.
  const markers = locations.map((position, i) => {
    const label = labels[i % labels.length];
    const marker = new google.maps.Marker({
      position,
      label,
    });

    // markers can only be keyboard focusable when they have click listeners
    // open info window when marker is clicked
    marker.addListener("click", () => {
      infoWindow.setContent(label);
      infoWindow.open(map, marker);
    });
    return marker;
  });

  // Add a marker clusterer to manage the markers.
  new MarkerClusterer({ markers, map });
}

const locations = [
  { lat: -31.56391, lng: 147.154312 },
  { lat: -33.718234, lng: 150.363181 },
  { lat: -33.727111, lng: 150.371124 },
  { lat: -33.848588, lng: 151.209834 },
  { lat: -33.851702, lng: 151.216968 },
  { lat: -34.671264, lng: 150.863657 },
  { lat: -35.304724, lng: 148.662905 },
  { lat: -36.817685, lng: 175.699196 },
  { lat: -36.828611, lng: 175.790222 },
  { lat: -37.75, lng: 145.116667 },
  { lat: -37.759859, lng: 145.128708 },
  { lat: -37.765015, lng: 145.133858 },
  { lat: -37.770104, lng: 145.143299 },
  { lat: -37.7737, lng: 145.145187 },
  { lat: -37.774785, lng: 145.137978 },
  { lat: -37.819616, lng: 144.968119 },
  { lat: -38.330766, lng: 144.695692 },
  { lat: -39.927193, lng: 175.053218 },
  { lat: -41.330162, lng: 174.865694 },
  { lat: -42.734358, lng: 147.439506 },
  { lat: -42.734358, lng: 147.501315 },
  { lat: -42.735258, lng: 147.438 },
  { lat: -43.999792, lng: 170.463352 },
];

CSS

/* Always set the map height explicitly to define the size of the div
       * element that contains the map. */
#map {
  height: 100%;
}

/* Optional: Makes the sample page fill the window. */
html,
body {
  height: 100%;
  margin: 0;
  padding: 0;
}

HTML

<!DOCTYPE html>
<html>
  <head>
    <title>Marker Clustering</title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
    <link rel="stylesheet" type="text/css" href="./style.css" />
    <script src="./index.js"></script>
  </head>
  <body>
    <div id="map"></div>

    <!-- Async script executes immediately and must be after any DOM elements used in callback. -->
    <script
      src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap&v=weekly"
      async
    ></script>
  </body>
</html>

Try Sample

As a simple illustration, this tutorial adds a set of markers to the map using the locations array. You can use other sources to get markers for your map. For more information, read the guide to creating markers.

Adding a marker clusterer

Follow the steps below to add a marker clusterer:

  1. Add the marker clustering library to your page or application. The library is available on NPM at @googlemaps/markerclusterer and in the repository on GitHub.

    NPM

    Install the latest version of the @googlemaps/markerclustererÍ library using NPM.

    npm install @googlemaps/markerclusterer

    CDN

    The script below loads the latest 1.x.x version of the library from the unpkg.com CDN.

    <script src="https://unpkg.com/@googlemaps/markerclusterer/dist/index.min.js"></script>
  2. Add a marker clusterer in your app.

    The code below adds a marker clusterer to the map.

    NPM

    import { MarkerClusterer } from "@googlemaps/markerclusterer";
    
    const markerCluster = new MarkerClusterer({ map, markers });

    CDN

    When accessed with the CDN, the library is available under the markerClusterer global.

    const markerCluster = new markerClusterer.MarkerClusterer({ map, markers });

    This sample passes the markers array to the MarkerClusterer.

  3. Customize the marker clusterer.

Learn more

You can view more complex examples of marker clustering in the repository on GitHub and read the reference documentation for the library.