Skip to main content

protocol

Register a custom protocol and intercept existing protocol requests.

Process: Main

An example of implementing a protocol that has the same effect as the file:// protocol:

const { app, protocol, net } = require('electron')

const path = require('node:path')
const url = require('node:url')

app.whenReady().then(() => {
  protocol.handle('atom', (request) => {
    const filePath = request.url.slice('atom://'.length)
    return net.fetch(url.pathToFileURL(path.join(__dirname, filePath)).toString())
  })
})
note

All methods unless specified can only be used after the ready event of the app module gets emitted.

Using protocol with a custom partition or session​

A protocol is registered to a specific Electron session object. If you don't specify a session, then your protocol will be applied to the default session that Electron uses. However, if you define a partition or session on your browserWindow's webPreferences, then that window will use a different session and your custom protocol will not work if you just use electron.protocol.XXX.

To have your custom protocol work in combination with a custom session, you need to register it to that session explicitly.

const { app, BrowserWindow, net, protocol, session } = require('electron')

const path = require('node:path')
const url = require('node:url')

app.whenReady().then(() => {
  const partition = 'persist:example'
  const ses = session.fromPartition(partition)

  ses.protocol.handle('atom', (request) => {
    const filePath = request.url.slice('atom://'.length)
    return net.fetch(url.pathToFileURL(path.resolve(__dirname, filePath)).toString())
  })

  const mainWindow = new BrowserWindow({ webPreferences: { partition } })
})

Protocol names​

RFC 3986 defines what a valid protocol name is:

Scheme names consist of a sequence of characters beginning with a letter and followed by any combination of letters, digits, plus ("+"), period ("."), or hyphen ("-"). Although schemes are case-insensitive, the canonical form is lowercase […].

Methods​

The protocol module has the following methods:

protocol.registerSchemesAsPrivileged(customSchemes)​

note

This method can only be used before the ready event of the app module gets emitted and can be called only once.

Registers the scheme as standard, secure, bypasses content security policy for resources, allows registering ServiceWorker, supports fetch API, streaming video/audio, and V8 code cache. Specify a privilege with the value of true to enable the capability.

An example of registering a privileged scheme, that bypasses Content Security Policy:

const { protocol } = require('electron')

protocol.registerSchemesAsPrivileged([
  { scheme: 'foo', privileges: { bypassCSP: true } }
])

A standard scheme adheres to what RFC 3986 calls generic URI syntax. For example http and https are standard schemes, while file is not.

Registering a scheme as standard allows relative and absolute resources to be resolved correctly when served. Otherwise the scheme will behave like the file protocol, but without the ability to resolve relative URLs.

For example when you load following page with custom protocol without registering it as standard scheme, the image will not be loaded because non-standard schemes can not recognize relative URLs:

<body>
  <img src='test.png'>
</body>

Registering a scheme as standard will allow access to files through the FileSystem API. Otherwise the renderer will throw a security error for the scheme.

By default web storage apis (localStorage, sessionStorage, webSQL, indexedDB, cookies) are disabled for non standard schemes. So in general if you want to register a custom protocol to replace the http protocol, you have to register it as a standard scheme.

Protocols that use streams (http and stream protocols) should set stream: true. The <video> and <audio> HTML elements expect protocols to buffer their responses by default. The stream flag configures those elements to correctly expect streaming responses.

protocol.handle(scheme, handler)​

  • scheme string - scheme to handle, for example https or my-app. This is the bit before the : in a URL.
  • handler Function<GlobalResponse | Promise<GlobalResponse>>

Register a protocol handler for scheme. Requests made to URLs with this scheme will delegate to this handler to determine what response should be sent.

Either a Response or a Promise<Response> can be returned.

Example:

const { app, net, protocol } = require('electron')

const path = require('node:path')
const { pathToFileURL } = require('node:url')

protocol.registerSchemesAsPrivileged([
  {
    scheme: 'app',
    privileges: {
      standard: true,
      secure: true,
      supportFetchAPI: true