# Updating Applications

There are several ways to update an Electron application. The easiest and
officially supported one is taking advantage of the built-in
[Squirrel](https://github.com/Squirrel) framework and
Electron's [autoUpdater](../api/auto-updater.md) module.

## Using `update.electronjs.org`

GitHub's Electron team maintains [update.electronjs.org], a free and open-source
webservice that Electron apps can use to self-update. The service is designed 
for Electron apps that meet the following criteria:

- App runs on macOS or Windows
- App has a public GitHub repository
- Builds are published to GitHub Releases
- Builds are code-signed

The easiest way to use this service is by installing [update-electron-app],
a Node.js module preconfigured for use with update.electronjs.org.

Install the module:

```sh
npm install update-electron-app
```

Invoke the updater from your app's main process file:

```js
require('update-electron-app')()
```

By default, this module will check for updates at app startup, then every ten 
minutes. When an update is found, it will automatically be downloaded in the background. When the download completes, a dialog is displayed allowing the user 
to restart the app.

If you need to customize your configuration, you can 
[pass options to `update-electron-app`][update-electron-app]
or 
[use the update service directly][update.electronjs.org].

## Using `electron-builder`

If your app is packaged with [`electron-builder`][electron-builder-lib] you can use the
[electron-updater] module, which does not require a server and allows for updates
from S3, GitHub or any other static file host. This sidesteps Electron's built-in
update mechanism, meaning that the rest of this documentation will not apply to
`electron-builder`'s updater.

## Deploying an Update Server

If you're developing a private Electron application, or if you're not
publishing releases to GitHub Releases, it may be necessary to run your own 
update server.

Depending on your needs, you can choose from one of these:

- [Hazel][hazel] – Update server for private or open-source apps which can be
deployed for free on [Now][now]. It pulls from [GitHub Releases][gh-releases]
and leverages the power of GitHub's CDN.
- [Nuts][nuts] – Also uses [GitHub Releases][gh-releases], but caches app
updates on disk and supports private repositories.
- [electron-release-server][electron-release-server] – Provides a dashboard for
handling releases and does not require releases to originate on GitHub.
- [Nucleus][nucleus] – A complete update server for Electron apps maintained by
Atlassian. Supports multiple applications and channels; uses a static file store
to minify server cost.

## Implementing Updates in Your App

Once you've deployed your update server, continue with importing the required
modules in your code. The following code might vary for different server
software, but it works like described when using
[Hazel](https://github.com/zeit/hazel).

**Important:** Please ensure that the code below will only be executed in
your packaged app, and not in development. You can use
[electron-is-dev](https://github.com/sindresorhus/electron-is-dev) to check for
the environment.

```javascript
const { app, autoUpdater, dialog } = require('electron')
```

Next, construct the URL of the update server and tell
[autoUpdater](../api/auto-updater.md) about it:

```javascript
const server = 'https://your-deployment-url.com'
const feed = `${server}/update/${process.platform}/${app.getVersion()}`

autoUpdater.setFeedURL(feed)
```

As the final step, check for updates. The example below will check every minute:

```javascript
setInterval(() => {
  autoUpdater.checkForUpdates()
}, 60000)
```

Once your application is [packaged](../tutorial/application-distribution.md),
it will receive an update for each new
[GitHub Release](https://help.github.com/articles/creating-releases/) that you
publish.

## Applying Updates

Now that you've configured the basic update mechanism for your application, you
need to ensure that the user will get notified when there's an update. This
can be achieved using the autoUpdater API
[events](../api/auto-updater.md#events):

```javascript
autoUpdater.on('update-downloaded', (event, releaseNotes, releaseName) => {
  const dialogOpts = {
    type: 'info',
    buttons: ['Restart', 'Later'],
    title: 'Application Update',
    message: process.platform === 'win32' ? releaseNotes : releaseName,
    detail: 'A new version has been downloaded. Restart the application to apply the updates.'
  }

  dialog.showMessageBox(dialogOpts, (response) => {
    if (response === 0) autoUpdater.quitAndInstall()
  })
})
```

Also make sure that errors are
[being handled](../api/auto-updater.md#event-error). Here's an example
for logging them to `stderr`:

```javascript
autoUpdater.on('error', message => {
  console.error('There was a problem updating the application')
  console.error(message)
})
```

[electron-builder-lib]: https://github.com/electron-userland/electron-builder
[electron-updater]: https://www.electron.build/auto-update
[now]: https://zeit.co/now
[hazel]: https://github.com/zeit/hazel
[nuts]: https://github.com/GitbookIO/nuts
[gh-releases]: https://help.github.com/articles/creating-releases/
[electron-release-server]: https://github.com/ArekSredzki/electron-release-server
[nucleus]: https://github.com/atlassian/nucleus
[update.electronjs.org]: https://github.com/electron/update.electronjs.org
[update-electron-app]: https://github.com/electron/update-electron-app