example of Electron splash window @ load

background.js

'use strict'

import { app, BrowserWindow, protocol } from 'electron'
import { createProtocol } from 'vue-cli-plugin-electron-builder/lib'
import installExtension, { VUEJS_DEVTOOLS } from 'electron-devtools-installer'

// --- CONTEXT MENU -----
const contextMenu = require('electron-context-menu')
contextMenu({
  prepend: (defaultActions, params, browserWindow) => []
})

// Keep a global reference of the window object, if you don't, the window will
// be closed automatically when the JavaScript object is garbage collected.
let win

// Scheme must be registered before the app is ready
protocol.registerSchemesAsPrivileged([{ scheme: 'app', privileges: { secure: true, standard: true } }])

app.commandLine.appendSwitch('disable-features', 'OutOfBlinkCors')

async function createWindow () {
  function showMainWin () {
    splash.destroy()
    win.show()
  }

  const image = require('electron').nativeImage
    .createFromPath('./src/assets/icons/png/64x64.png')

  // Create the browser window.
  win = new BrowserWindow({
    titleBarStyle: 'hidden',
    width: 460
    height: 800,
    backgroundColor: '#fff',
    icon: image,
    webPreferences: {
      nodeIntegration: true,
      webSecurity: false,
      devTools: !!(process.env.WEBPACK_DEV_SERVER_URL),
      enableRemoteModule: true
    },
    show: false // don't show the main window YET
  })
  win.setMenuBarVisibility(false)

  // create a new `splash`-Window
  const splash = new BrowserWindow(
    {
      width: 555,
      height: 555,
      icon: image,
      transparent: true,
      frame: false,
      alwaysOnTop: true
    })

  if (process.env.WEBPACK_DEV_SERVER_URL) {
    // Load the url of the dev server if in development mode
    splash.loadURL(process.env.WEBPACK_DEV_SERVER_URL + 'splash.html')
    win.loadURL(process.env.WEBPACK_DEV_SERVER_URL).then(() => {
      // (!!!) otherwise devTools won't work
      if (!process.env.IS_TEST) {
        setTimeout(() => win.webContents.openDevTools(), 5555)
      }
    })
  } else {
    createProtocol('app')
    splash.loadURL('app://./splash.html')
    // Load the index.html when not in development
    win.loadURL('app://./index.html')
  }

  win.once('ready-to-show', () => {
    setTimeout(() => showMainWin(), 88)
  })
  
  ...
  
  
// This method will be called when Electron has finished
// initialization and is ready to create browser windows.
// Some APIs can only be used after this event occurs.
app.on('ready', async () => {
  if (isDevelopment && !process.env.IS_TEST) {
    // Install Vue Devtools
    try {
      const vueDT = await installExtension(VUEJS_DEVTOOLS)
    } catch (e) {
      console.error('Vue Devtools failed to install:', e.toString())
    }
  }
  createWindow()
})

Have you tried putting await on all four instances like this

if (process.env.WEBPACK_DEV_SERVER_URL) {
    // Load the url of the dev server if in development mode
    await splash.loadURL(process.env.WEBPACK_DEV_SERVER_URL + 'splash.html')
    await win.loadURL(process.env.WEBPACK_DEV_SERVER_URL)
    if (!process.env.IS_TEST) {
      setTimeout(() => win.webContents.openDevTools(), 5555)
    }
  } else {
    await createProtocol('app')
    await splash.loadURL('app://./splash.html')
    // Load the index.html when not in development
    win.loadURL('app://./index.html')
  }

Just adding it here should work I think:

await win.loadURL(process.env.WEBPACK_DEV_SERVER_URL)

Have you tried putting await on all four instances like this

if (process.env.WEBPACK_DEV_SERVER_URL) {
    // Load the url of the dev server if in development mode
    await splash.loadURL(process.env.WEBPACK_DEV_SERVER_URL + 'splash.html')
    await win.loadURL(process.env.WEBPACK_DEV_SERVER_URL)
    if (!process.env.IS_TEST) {
      setTimeout(() => win.webContents.openDevTools(), 5555)
    }
  } else {
    await createProtocol('app')
    await splash.loadURL('app://./splash.html')
    // Load the index.html when not in development
    win.loadURL('app://./index.html')
  }

I've tried. When I add at least one "await" the process freezes without any warnings/errors somewhere after "await win.loadURL..."

Just adding it here should work I think:

await win.loadURL(process.env.WEBPACK_DEV_SERVER_URL)

Unfortunately it doesn't, was the first thing I've tried

What about this:

win.loadURL(process.env.WEBPACK_DEV_SERVER_URL).then(() => {
  if (!process.env.IS_TEST) {
    setTimeout(() => win.webContents.openDevTools(), 5555)
  }
})

What about this:

win.loadURL(process.env.WEBPACK_DEV_SERVER_URL).then(() => {
  if (!process.env.IS_TEST) {
    setTimeout(() => win.webContents.openDevTools(), 5555)
  }
})

wow, thanks a lot!!! now it finally works 🚀
can't believe I haven't noticed that myself