> For the complete documentation index, see [llms.txt](https://docs.mapbox.com/mapbox-gl-js/ja/llms.txt)
# Add markers to a web map with a symbol layer
This example visualizes point features on a map using a [`symbol`](https://docs.mapbox.com/style-spec/reference/layers/#symbol) layer.
Upon loading, the map uses [`loadImage`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#loadimage) to load an image into the map's style, [`addSource`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#addsource) to add a GeoJSON collection of points as a data source, and then [`addLayer`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#addlayer) to draw the image and label on the map at each point location.
> **Note (warning): Supported File Types**
>
> Only `.png`, `.jpg` and `.webp` formats are supported when loading images into a style at runtime using [`map.loadImage()`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#loadimage). Other file types like `.svg` are not supported.
> **Note: Managing symbol layers with Mapbox Studio**
>
> Managing symbol layers in runtime code can become complex. Consider building a custom style in [Mapbox Studio](https://studio.mapbox.com/) instead — you can upload your data and marker images directly, style them visually, and then load the finished style in GL JS with a single `style` URL. Mapbox Studio also supports uploading SVG (vector) images, which are not supported by [`loadImage`](https://docs.mapbox.com/mapbox-gl-js/ja/api/map/#map#loadimage) at runtime.
> Example code:
**JavaScript**
```html
Add markers to a web map with a symbol layer
```
**React**
```jsx
import React, { useEffect, useRef } from 'react';
import * as mapboxgl from 'mapbox-gl/esm';
import 'mapbox-gl/dist/mapbox-gl.css';
const MapboxExample = () => {
const mapContainerRef = useRef();
const mapRef = useRef();
useEffect(() => {
mapRef.current = new mapboxgl.Map({
// TO MAKE THE MAP APPEAR YOU MUST
// ADD YOUR ACCESS TOKEN FROM
// https://account.mapbox.com
accessToken: 'YOUR_MAPBOX_ACCESS_TOKEN',
container: mapContainerRef.current,
style: 'mapbox://styles/mapbox/standard',
bounds: [
[-128.99107, 22.62724],
[-63.35107, 50.26125]
]
});
mapRef.current.on('load', () => {
mapRef.current.loadImage(
'https://docs.mapbox.com/mapbox-gl-js/assets/custom_marker.png',
(error, image) => {
if (error) throw error;
mapRef.current.addImage('custom-marker', image);
mapRef.current.addSource('points', {
type: 'geojson',
data: {
type: 'FeatureCollection',
features: [
{
type: 'Feature',
geometry: {
type: 'Point',
coordinates: [-77.03238901390978, 38.913188059745586]
},
properties: {
title: 'Mapbox DC'
}
},
{
type: 'Feature',
geometry: {
type: 'Point',
coordinates: [-122.414, 37.776]
},
properties: {
title: 'Mapbox SF'
}
}
]
}
});
mapRef.current.addLayer({
id: 'points',
type: 'symbol',
source: 'points',
layout: {
'icon-image': 'custom-marker',
'text-field': ['get', 'title'],
'text-font': ['Open Sans Semibold', 'Arial Unicode MS Bold'],
'text-offset': [0, 1.25],
'text-anchor': 'top'
}
});
}
);
});
}, []);
return ;
};
export default MapboxExample;
```
> **Related content (example): [Alternative Marker Technique](https://docs.mapbox.com/mapbox-gl-js/ja/example/add-a-marker/)**
>
> See **Add a default marker to a web map** for a less complex approach to visualizing point features using the `Marker` class.