# API Contract

Breaking changes will be documented here, and deprecation warnings added to JS code where possible, at least [one major version](../tutorial/electron-versioning.md#semver) before the change is made.

# `FIXME` comments

The `FIXME` string is used in code comments to denote things that should be fixed for future releases. See https://github.com/electron/electron/search?q=fixme


# Planned Breaking API Changes (4.0)

The following list includes the breaking API changes planned for Electron 4.0.

## `app.makeSingleInstance`

```js
// Deprecated
app.makeSingleInstance(function (argv, cwd) {

})
// Replace with
app.requestSingleInstanceLock()
app.on('second-instance', function (argv, cwd) {

})
```

## `app.releaseSingleInstance`

```js
// Deprecated
app.releaseSingleInstance()
// Replace with
app.releaseSingleInstanceLock()
```


# Planned Breaking API Changes (3.0)

The following list includes the breaking API changes planned for Electron 3.0.

## `app`

```js
// Deprecated
app.getAppMemoryInfo()
// Replace with
app.getAppMetrics()
```

## `BrowserWindow`

```js
// Deprecated
let optionsA = {webPreferences: {blinkFeatures: ''}}
let windowA = new BrowserWindow(optionsA)
// Replace with
let optionsB = {webPreferences: {enableBlinkFeatures: ''}}
let windowB = new BrowserWindow(optionsB)

// Deprecated
window.on('app-command', (e, cmd) => {
  if (cmd === 'media-play_pause') {
    // do something
  }
})
// Replace with
window.on('app-command', (e, cmd) => {
  if (cmd === 'media-play-pause') {
    // do something
  }
})
```

## `clipboard`

```js
// Deprecated
clipboard.readRtf()
// Replace with
clipboard.readRTF()

// Deprecated
clipboard.writeRtf()
// Replace with
clipboard.writeRTF()

// Deprecated
clipboard.readHtml()
// Replace with
clipboard.readHTML()

// Deprecated
clipboard.writeHtml()
// Replace with
clipboard.writeHTML()
```

## `crashReporter`

```js
// Deprecated
crashReporter.start({
  companyName: 'Crashly',
  submitURL: 'https://crash.server.com',
  autoSubmit: true
})
// Replace with
crashReporter.start({
  companyName: 'Crashly',
  submitURL: 'https://crash.server.com',
  uploadToServer: true
})
```

## `nativeImage`

```js
// Deprecated
nativeImage.createFromBuffer(buffer, 1.0)
// Replace with
nativeImage.createFromBuffer(buffer, {
  scaleFactor: 1.0
})
```

## `screen`

```js
// Deprecated
screen.getMenuBarHeight()
// Replace with
screen.getPrimaryDisplay().workArea
```

## `session`

```js
// Deprecated
ses.setCertificateVerifyProc(function (hostname, certificate, callback) {
  callback(true)
})
// Replace with
ses.setCertificateVerifyProc(function (request, callback) {
  callback(0)
})
```

## `Tray`

```js
// Deprecated
tray.setHighlightMode(true)
// Replace with
tray.setHighlightMode('on')

// Deprecated
tray.setHighlightMode(false)
// Replace with
tray.setHighlightMode('off')
```

## `webContents`

```js
// Deprecated
webContents.openDevTools({detach: true})
// Replace with
webContents.openDevTools({mode: 'detach'})
```

## `webFrame`

```js
// Deprecated
webFrame.registerURLSchemeAsSecure('app')
// Replace with
protocol.registerStandardSchemes(['app'], {secure: true})

// Deprecated
webFrame.registerURLSchemeAsPrivileged('app', {secure: true})
// Replace with
protocol.registerStandardSchemes(['app'], {secure: true})
```

## Node Headers URL

This is the URL specified as `disturl` in a `.npmrc` file or as the `--dist-url`
command line flag when building native Node modules.

Deprecated: https://atom.io/download/atom-shell

Replace with: https://atom.io/download/electron


# Breaking API Changes (2.0)

The following list includes the breaking API changes made in Electron 2.0.

## `BrowserWindow`

```js
// Deprecated
let optionsA = {titleBarStyle: 'hidden-inset'}
let windowA = new BrowserWindow(optionsA)
// Replace with
let optionsB = {titleBarStyle: 'hiddenInset'}
let windowB = new BrowserWindow(optionsB)
```

## `menu`

```js
// Removed
menu.popup(browserWindow, 100, 200, 2)
// Replaced with
menu.popup(browserWindow, {x: 100, y: 200, positioningItem: 2})
```

## `nativeImage`

```js
// Removed
nativeImage.toPng()
// Replaced with
nativeImage.toPNG()

// Removed
nativeImage.toJpeg()
// Replaced with
nativeImage.toJPEG()
```

## `process`

* `process.versions.electron` and `process.version.chrome` will be made
  read-only properties for consistency with the other `process.versions`
  properties set by Node.

## `webContents`

```js
// Removed
webContents.setZoomLevelLimits(1, 2)
// Replaced with
webContents.setVisualZoomLevelLimits(1, 2)
```

## `webFrame`

```js
// Removed
webFrame.setZoomLevelLimits(1, 2)
// Replaced with
webFrame.setVisualZoomLevelLimits(1, 2)
```

## `<webview>`

```js
// Removed
webview.setZoomLevelLimits(1, 2)
// Replaced with
webview.setVisualZoomLevelLimits(1, 2)
```

## Duplicate ARM Assets

Each Electron release includes two identical ARM builds with slightly different
filenames, like `electron-v1.7.3-linux-arm.zip` and
`electron-v1.7.3-linux-armv7l.zip`. The asset with the `v7l` prefix was added
to clarify to users which ARM version it supports, and to disambiguate it from
future armv6l and arm64 assets that may be produced.

The file _without the prefix_ is still being published to avoid breaking any
setups that may be consuming it. Starting at 2.0, the un-prefixed file will
no longer be published.

For details, see
[6986](https://github.com/electron/electron/pull/6986)
and
[7189](https://github.com/electron/electron/pull/7189).