Add a custom legend

  • This tutorial demonstrates how to create and add a legend to a Google Map using custom controls.

  • The legend provides information about custom markers, such as parking, libraries, and info points, displayed on the map.

  • It leverages HTML for structure, CSS for styling, and JavaScript/TypeScript for dynamic content and map interaction.

  • You can customize the legend's appearance (font, background, border) and position (e.g., right-bottom) as needed.

  • The legend content is dynamically generated based on the defined marker styles, ensuring it reflects the map's markers.

Overview

Learn how to create a legend on a Google map through this tutorial. Legends generally describe the symbols and markers on a map. You can create them using the positioning feature of custom controls.

The map below contains a legend that provides information about three different custom markers on the map.

The sections below explain the main steps to create a legend.

See the Complete code example section for the full code.

Create the legend container

Create the legend container by adding a div to the gmp-map element. Use control slotting to set the position of the legend. Read more about control position options.

<gmp-map center="-33.91722,151.23064" zoom="16.5" map-id="DEMO_MAP_ID">
    <div id="legend" slot="control-inline-start-block-start"></div>
</gmp-map>

Apply styles to set the visual appearance of the legend. This example styles the legend container, title, and item.

#legend {
    background-color: #fff;
    width: 15em;
    margin: 1em;
    border-radius: 8px;
    font-family: Roboto, Arial, sans-serif;
    overflow: hidden;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3);
}

.legend-item {
    margin: 0.5em 1em;
    display: flex;
    flex-direction: row;
    align-items: center;
    padding-bottom: 0.5em;
}

.legend-icon {
    margin-right: 1em;
    font-size: 24px;
}

.legend-text {
    font-size: 1.5em;
}

Add the legend content

The makeLegend() function programmatically builds a visual map legend and inserts it into the page's DOM. Here is how it works:

  1. Imports the Library: It dynamically imports the PinElement class from the Maps SDK (await google.maps.importLibrary('marker')).
const { PinElement } = await google.maps.importLibrary('marker');
  1. Prepares the Container: It grabs the existing empty <div id="legend"> from the HTML and prepends a "Legend" title element to it.
const legend = document.getElementById('legend')!;

const title = document.createElement('div');
title.innerText = 'Legend';
title.classList.add('title');
legend.appendChild(title);
  1. Iterates Over the Configurations: It loops through the icons configuration object to generate a row for each item (Parking, Library, Info). The helper function looks like this:

async function makeLegend() {
    const { PinElement } = await google.maps.importLibrary('marker');

    const legend = document.getElementById('legend');

    const title = document.createElement('div');
    title.innerText = 'Legend';
    title.classList.add('title');
    legend.appendChild(title);

    for (const type of Object.values(icons)) {
        const wrapper = document.createElement('div');
        wrapper.classList.add('legend-item');

        const pin = new PinElement({
            background: type.color,
            borderColor: type.color,
            glyphSrc: new URL(
                `data:image/svg+xml;charset=UTF-8,${encodeURIComponent(type.icon)}`
            ),
            scale: 1.0,
        });

        // PinElement extends HTMLElement directly, so we can append it directly!
        const pinContainer = document.createElement('div');
        pinContainer.classList.add('legend-icon');
        pinContainer.appendChild(pin);

        const txt = document.createElement('div');
        txt.classList.add('legend-text');
        txt.innerText = type.name;

        wrapper.appendChild(pinContainer);
        wrapper.appendChild(txt);
        legend.appendChild(wrapper);
    }
}

See Style point data features for another example of a programmatically generated legend.

Complete code example

The section below displays the entire code you need to create the map and legend in this tutorial.

TypeScript

const parkingSvg = `<svg fill="white" xmlns="http://www.w3.org/2000/svg" height="24" viewBox="0 0 24 24" width="24"><path d="M0 0h24v24H0z" fill="none"/><path d="M13 3H6v18h4v-6h3c3.31 0 6-2.69 6-6s-2.69-6-6-6zm.2 8H10V7h3.2c1.1 0 2 .9 2 2s-.9 2-2 2z"/></svg>`;
const librarySvg = `<svg fill="white" xmlns="http://www.w3.org/2000/svg" height="24" viewBox="0 0 24 24" width="24"><path d="M0 0h24v24H0z" fill="none"/><path d="M12 11.55C9.64 9.35 6.48 8 3 8v11c3.48 0 6.64 1.35 9 3.55 2.36-2.19 5.52-3.55 9-3.55V8c-3.48 0-6.64 1.35-9 3.55zM12 8c1.66 0 3-1.34 3-3s-1.34-3-3-3-3 1.34-3 3 1.34 3 3 3z"/></svg>`;
const infoSvg = `<svg fill="white" xmlns="http://www.w3.org/2000/svg" height="24" viewBox="0 0 24 24" width="24"><path d="M0 0h24v24H0z" fill="none"/><path d="M12 2C6.48 2 2 6.48 2 12s4.48 10 10 10 10-4.48 10-10S17.52 2 12 2zm1 15h-2v-6h2v6zm0-8h-2V7h2v2z"/></svg>`;

const icons: Record<string, { name: string; icon: string; color: string }> = {
    parking: {
        name: 'Parking',
        icon: parkingSvg,
        color: '#1E88E5', // Blue
    },
    library: {
        name: 'Library',
        icon: librarySvg,
        color: '#43A047', // Green
    },
    info: {
        name: 'Info',
        icon: infoSvg,
        color: '#E53935', // Red
    },
};

async function init(): Promise<void> {
    const [{ AdvancedMarkerElement, PinElement }, { event }] =
        await Promise.all([
            google.maps.importLibrary('marker'),
            google.maps.importLibrary('core'),
            google.maps.importLibrary('maps'),
        ]);

    const mapElement = document.querySelector('gmp-map')!;
    const innerMap = mapElement.innerMap;

    // Wait for the map to load before building the legend.
    event.addListenerOnce(innerMap, 'idle', () => {
        void makeLegend();
    });

    const features = [
        {
            position: { lat: -33.91721, lng: 151.2263 },
            type: 'info',
        },
        {
            position: { lat: -33.91539, lng: 151.2282 },
            type: 'info',
        },
        {
            position: { lat: -33.91747, lng: 151.22912 },
            type: 'info',
        },
        {
            position: { lat: -33.9191, lng: 151.22907 },
            type: 'info',
        },
        {
            position: { lat: -33.91725, lng: 151.23011 },
            type: 'info',
        },
        {
            position: { lat: -33.91872, lng: 151.23089 },
            type: 'info',
        },
        {
            position: { lat: -33.91784, lng: 151.23094 },
            type: 'info',
        },
        {
            position: { lat: -33.91682, lng: 151.23149 },
            type: 'info',
        },
        {
            position: { lat: -33.9179, lng: 151.23463 },
            type: 'info',
        },
        {
            position: { lat: -33.91666, lng: 151.23468 },
            type: 'info',
        },
        {
            position: { lat: -33.916988, lng: 151.23364 },
            type: 'info',
        },
        {
            position: { lat: -33.91662347903106, lng: 151.22879464019775 },
            type: 'parking',
        },
        {
            position: { lat: -33.916365282092855, lng: 151.22937399734496 },
            type: 'parking',
        },
        {
            position: { lat: -33.91665018901448, lng: 151.2282474695587 },
            type: 'parking',
        },
        {
            position: { lat: -33.919543720969806, lng: 151.23112279762267 },
            type: 'parking',
        },
        {
            position: { lat: -33.91608037421864, lng: 151.23288232673644 },
            type: 'parking',
        },
        {
            position: { lat: -33.91851096391805, lng: 151.2344058214569 },
            type: 'parking',
        },
        {
            position: { lat: -33.91818154739766, lng: 151.2346203981781 },
            type: 'parking',
        },
        {
            position: { lat: -33.91727341958453, lng: 151.23348314155578 },
            type: 'library',
        },
    ];

    for (const feature of features) {
        const iconData = icons[feature.type];

        const pin = new PinElement({
            background: iconData.color,
            borderColor: iconData.color,
            glyphSrc: new URL(
                `data:image/svg+xml;charset=UTF-8,${encodeURIComponent(iconData.icon)}`
            ),
            scale: 1.5,
        });

        const marker = new AdvancedMarkerElement({
            position: feature.position,
            title: iconData.name,
        });

        marker.append(pin);
        mapElement.append(marker);
    }
}

async function makeLegend() {
    const { PinElement } = await google.maps.importLibrary('marker');

    const legend = document.getElementById('legend')!;

    const title = document.createElement('div');
    title.innerText = 'Legend';
    title.classList.add('title');
    legend.appendChild(title);

    for (const type of Object.values(icons)) {
        const wrapper = document.createElement('div');
        wrapper.classList.add('legend-item');

        const pin = new PinElement({
            background: type.color,
            borderColor: type.color,
            glyphSrc: new URL(
                `data:image/svg+xml;charset=UTF-8,${encodeURIComponent(type.icon)}`
            ),
            scale: 1.0,
        });

        // PinElement extends HTMLElement directly, so we can append it directly!
        const pinContainer = document.createElement('div');
        pinContainer.classList.add('legend-icon');
        pinContainer.appendChild(pin);

        const txt = document.createElement('div');
        txt.classList.add('legend-text');
        txt.innerText = type.name;

        wrapper.appendChild(pinContainer);
        wrapper.appendChild(txt);
        legend.appendChild(wrapper);
    }
}

void init();

JavaScript

const parkingSvg = `<svg fill="white" xmlns="http://www.w3.org/2000/svg" height="24" viewBox="0 0 24 24" width="24"><path d="M0 0h24v24H0z" fill="none"/><path d="M13 3H6v18h4v-6h3c3.31 0 6-2.69 6-6s-2.69-6-6-6zm.2 8H10V7h3.2c1.1 0 2 .9 2 2s-.9 2-2 2z"/></svg>`;
const librarySvg = `<svg fill="white" xmlns="http://www.w3.org/2000/svg" height="24" viewBox="0 0 24 24" width="24"><path d="M0 0h24v24H0z" fill="none"/><path d="M12 11.55C9.64 9.35 6.48 8 3 8v11c3.48 0 6.64 1.35 9 3.55 2.36-2.19 5.52-3.55 9-3.55V8c-3.48 0-6.64 1.35-9 3.55zM12 8c1.66 0 3-1.34 3-3s-1.34-3-3-3-3 1.34-3 3 1.34 3 3 3z"/></svg>`;
const infoSvg = `<svg fill="white" xmlns="http://www.w3.org/2000/svg" height="24" viewBox="0 0 24 24" width="24"><path d="M0 0h24v24H0z" fill="none"/><path d="M12 2C6.48 2 2 6.48 2 12s4.48 10 10 10 10-4.48 10-10S17.52 2 12 2zm1 15h-2v-6h2v6zm0-8h-2V7h2v2z"/></svg>`;

const icons = {
    parking: {
        name: 'Parking',
        icon: parkingSvg,
        color: '#1E88E5', // Blue
    },
    library: {
        name: 'Library',
        icon: librarySvg,
        color: '#43A047', // Green
    },
    info: {
        name: 'Info',
        icon: infoSvg,
        color: '#E53935', // Red
    },
};

async function init() {
    const [{ AdvancedMarkerElement, PinElement }, { event }] =
        await Promise.all([
            google.maps.importLibrary('marker'),
            google.maps.importLibrary('core'),
            google.maps.importLibrary('maps'),
        ]);

    const mapElement = document.querySelector('gmp-map');
    const innerMap = mapElement.innerMap;

    // Wait for the map to load before building the legend.
    event.addListenerOnce(innerMap, 'idle', () => {
        void makeLegend();
    });

    const features = [
        {
            position: { lat: -33.91721, lng: 151.2263 },
            type: 'info',
        },
        {
            position: { lat: -33.91539, lng: 151.2282 },
            type: 'info',
        },
        {
            position: { lat: -33.91747, lng: 151.22912 },
            type: 'info',
        },
        {
            position: { lat: -33.9191, lng: 151.22907 },
            type: 'info',
        },
        {
            position: { lat: -33.91725, lng: 151.23011 },
            type: 'info',
        },
        {
            position: { lat: -33.91872, lng: 151.23089 },
            type: 'info',
        },
        {
            position: { lat: -33.91784, lng: 151.23094 },
            type: 'info',
        },
        {
            position: { lat: -33.91682, lng: 151.23149 },
            type: 'info',
        },
        {
            position: { lat: -33.9179, lng: 151.23463 },
            type: 'info',
        },
        {
            position: { lat: -33.91666, lng: 151.23468 },
            type: 'info',
        },
        {
            position: { lat: -33.916988, lng: 151.23364 },
            type: 'info',
        },
        {
            position: { lat: -33.91662347903106, lng: 151.22879464019775 },
            type: 'parking',
        },
        {
            position: { lat: -33.916365282092855, lng: 151.22937399734496 },
            type: 'parking',
        },
        {
            position: { lat: -33.91665018901448, lng: 151.2282474695587 },
            type: 'parking',
        },
        {
            position: { lat: -33.919543720969806, lng: 151.23112279762267 },
            type: 'parking',
        },
        {
            position: { lat: -33.91608037421864, lng: 151.23288232673644 },
            type: 'parking',
        },
        {
            position: { lat: -33.91851096391805, lng: 151.2344058214569 },
            type: 'parking',
        },
        {
            position: { lat: -33.91818154739766, lng: 151.2346203981781 },
            type: 'parking',
        },
        {
            position: { lat: -33.91727341958453, lng: 151.23348314155578 },
            type: 'library',
        },
    ];

    for (const feature of features) {
        const iconData = icons[feature.type];

        const pin = new PinElement({
            background: iconData.color,
            borderColor: iconData.color,
            glyphSrc: new URL(
                `data:image/svg+xml;charset=UTF-8,${encodeURIComponent(iconData.icon)}`
            ),
            scale: 1.5,
        });

        const marker = new AdvancedMarkerElement({
            position: feature.position,
            title: iconData.name,
        });

        marker.append(pin);
        mapElement.append(marker);
    }
}

async function makeLegend() {
    const { PinElement } = await google.maps.importLibrary('marker');

    const legend = document.getElementById('legend');

    const title = document.createElement('div');
    title.innerText = 'Legend';
    title.classList.add('title');
    legend.appendChild(title);

    for (const type of Object.values(icons)) {
        const wrapper = document.createElement('div');
        wrapper.classList.add('legend-item');

        const pin = new PinElement({
            background: type.color,
            borderColor: type.color,
            glyphSrc: new URL(
                `data:image/svg+xml;charset=UTF-8,${encodeURIComponent(type.icon)}`
            ),
            scale: 1.0,
        });

        // PinElement extends HTMLElement directly, so we can append it directly!
        const pinContainer = document.createElement('div');
        pinContainer.classList.add('legend-icon');
        pinContainer.appendChild(pin);

        const txt = document.createElement('div');
        txt.classList.add('legend-text');
        txt.innerText = type.name;

        wrapper.appendChild(pinContainer);
        wrapper.appendChild(txt);
        legend.appendChild(wrapper);
    }
}

void init();

CSS

html,
body {
    height: 100%;
    margin: 0;
    padding: 0;
}

#legend {
    background-color: #fff;
    width: 15em;
    margin: 1em;
    border-radius: 8px;
    font-family: Roboto, Arial, sans-serif;
    overflow: hidden;
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.3);
}

.title {
    padding: 0.5em 1em;
    font-weight: bold;
    font-size: 1.5em;
    margin-bottom: 0.5em;
    background-color: rgb(66, 133, 244);
    color: white;
    box-sizing: border-box;
}

.legend-item {
    margin: 0.5em 1em;
    display: flex;
    flex-direction: row;
    align-items: center;
    padding-bottom: 0.5em;
}

.legend-icon {
    margin-right: 1em;
    font-size: 24px;
}

.legend-text {
    font-size: 1.5em;
}

HTML

<html>
    <head>
        <title>Custom Legend</title>

        <link rel="stylesheet" type="text/css" href="./style.css" />
        <script type="module" src="./index.js"></script>

        <script>
            // prettier-ignore
            (g=>{var h,a,k,p="The Google Maps JavaScript API",c="google",l="importLibrary",q="__ib__",m=document,b=window;b=b[c]||(b[c]={});var d=b.maps||(b.maps={}),r=new Set,e=new URLSearchParams,u=()=>h||(h=new Promise(async(f,n)=>{await (a=m.createElement("script"));e.set("libraries",[...r]+"");for(k in g)e.set(k.replace(/[A-Z]/g,t=>"_"+t[0].toLowerCase()),g[k]);e.set("callback",c+".maps."+q);a.src=`https://maps.${c}apis.com/maps/api/js?`+e;d[q]=f;a.onerror=()=>h=n(Error(p+" could not load."));a.nonce=m.querySelector("script[nonce]")?.nonce||"";m.head.append(a)}));d[l]?console.warn(p+" only loads once. Ignoring:",g):d[l]=(f,...n)=>r.add(f)&&u().then(()=>d[l](f,...n))})({
                key: "GOOGLE_MAPS_API_KEY"
            });
        </script>
    </head>
    <body>
        <gmp-map center="-33.91722,151.23064" zoom="16.5" map-id="DEMO_MAP_ID">
            <div id="legend" slot="control-inline-start-block-start"></div>
        </gmp-map>
    </body>
</html>