# desktopCapturer
> Access information about media sources that can be used to capture audio and
> video from the desktop using the [`navigator.mediaDevices.getUserMedia`][] API.
Process: [Main](../glossary.md#main-process)
The following example shows how to capture video from a desktop window whose
title is `Electron`:
```js
// main.js
const { app, BrowserWindow, desktopCapturer, session } = require('electron')
app.whenReady().then(() => {
const mainWindow = new BrowserWindow()
session.defaultSession.setDisplayMediaRequestHandler((request, callback) => {
desktopCapturer.getSources({ types: ['screen'] }).then((sources) => {
// Grant access to the first screen found.
callback({ video: sources[0], audio: 'loopback' })
})
})
mainWindow.loadFile('index.html')
})
```
```js
// renderer.js
const startButton = document.getElementById('startButton')
const stopButton = document.getElementById('stopButton')
const video = document.querySelector('video')
startButton.addEventListener('click', () => {
navigator.mediaDevices.getDisplayMedia({
audio: true,
video: {
width: 320,
height: 240,
frameRate: 30
}
}).then(stream => {
video.srcObject = stream
video.onloadedmetadata = (e) => video.play()
}).catch(e => console.log(e))
})
stopButton.addEventListener('click', () => {
video.pause()
})
```
```html
<!-- index.html -->
<html>
<meta http-equiv="content-security-policy" content="script-src 'self' 'unsafe-inline'" />
<body>
<button id="startButton" class="button">Start</button>
<button id="stopButton" class="button">Stop</button>
<video width="320" height="240" autoplay></video>
<script src="renderer.js"></script>
</body>
</html>
```
See [`navigator.mediaDevices.getDisplayMedia`](https://developer.mozilla.org/en-US/docs/Web/API/MediaDevices/getDisplayMedia) for more information.
**Note:** `navigator.mediaDevices.getDisplayMedia` does not permit the use of `deviceId` for
selection of a source - see [specification](https://w3c.github.io/mediacapture-screen-share/#constraints).
## Methods
The `desktopCapturer` module has the following methods:
### `desktopCapturer.getSources(options)`
* `options` Object
* `types` string[] - An array of strings that lists the types of desktop sources
to be captured, available types can be `screen` and `window`.
* `thumbnailSize` [Size](structures/size.md) (optional) - The size that the media source thumbnail
should be scaled to. Default is `150` x `150`. Set width or height to 0 when you do not need
the thumbnails. This will save the processing time required for capturing the content of each
window and screen.
* `fetchWindowIcons` boolean (optional) - Set to true to enable fetching window icons. The default
value is false. When false the appIcon property of the sources return null. Same if a source has
the type screen.
Returns `Promise<DesktopCapturerSource[]>` - Resolves with an array of [`DesktopCapturerSource`](structures/desktop-capturer-source.md) objects, each `DesktopCapturerSource` represents a screen or an individual window that can be captured.
**Note** Capturing the screen contents requires user consent on macOS 10.15 Catalina or higher,
which can detected by [`systemPreferences.getMediaAccessStatus`][].
[`navigator.mediaDevices.getUserMedia`]: https://developer.mozilla.org/en/docs/Web/API/MediaDevices/getUserMedia
[`systemPreferences.getMediaAccessStatus`]: system-preferences.md#systempreferencesgetmediaaccessstatusmediatype-windows-macos
## Caveats
`navigator.mediaDevices.getUserMedia` does not work on macOS for audio capture due to a fundamental limitation whereby apps that want to access the system's audio require a [signed kernel extension](https://developer.apple.com/library/archive/documentation/Security/Conceptual/System_Integrity_Protection_Guide/KernelExtensions/KernelExtensions.html). Chromium, and by extension Electron, does not provide this.
It is possible to circumvent this limitation by capturing system audio with another macOS app like Soundflower and passing it through a virtual audio input device. This virtual device can then be queried with `navigator.mediaDevices.getUserMedia`.