Concurrent requests to the same URLs are not sent at the same time

main.js

// Modules to control application life and create native browser window
const { app, BrowserWindow } = require('electron')
const path = require('node:path')

function createWindow () {
  // Create the browser window.
  const mainWindow = new BrowserWindow({
    width: 800,
    height: 600,
  })

  // and load the index.html of the app.
  mainWindow.loadURL('https://example.com')

  // Open the DevTools.
  // mainWindow.webContents.openDevTools()
}

// 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.whenReady().then(() => {
  createWindow()

  app.on('activate', function () {
    // On macOS it's common to re-create a window in the app when the
    // dock icon is clicked and there are no other windows open.
    if (BrowserWindow.getAllWindows().length === 0) createWindow()
  })
})

// Quit when all windows are closed, except on macOS. There, it's common
// for applications and their menu bar to stay active until the user quits
// explicitly with Cmd + Q.
app.on('window-all-closed', function () {
  if (process.platform !== 'darwin') app.quit()
})

// In this file you can include the rest of your app's specific main process
// code. You can also put them in separate files and require them here.

package.json

{
  "name": "kindhearted-debt-prepare-ewi18",
  "productName": "kindhearted-debt-prepare-ewi18",
  "description": "My Electron application description",
  "keywords": [],
  "main": "./main.js",
  "version": "1.0.0",
  "author": "kadir",
  "scripts": {
    "start": "electron ."
  },
  "dependencies": {},
  "devDependencies": {
    "electron": "30.0.2"
  }
}

preload.js

/**
 * The preload script runs before `index.html` is loaded
 * in the renderer. It has access to web APIs as well as
 * Electron's renderer process modules and some polyfilled
 * Node.js functions.
 *
 * https://www.electronjs.org/docs/latest/tutorial/sandbox
 */
window.addEventListener('DOMContentLoaded', () => {
  const replaceText = (selector, text) => {
    const element = document.getElementById(selector)
    if (element) element.innerText = text
  }

  for (const type of ['chrome', 'node', 'electron']) {
    replaceText(`${type}-version`, process.versions[type])
  }
})

Paste the following code into the console.

for(i=0;i<15;i++) {
    fetch("https://jsonplaceholder.typicode.com/todos/1").then(r => r.text())
}

In the Network tab you will see that each request is waiting for the previous one.