How to set electron UserAgent

Just use an option object when loading the URL.

function createWindow () {
   win = new BrowserWindow({width: 800, height: 600});
   win.loadURL('http://www.whoishostingthis.com/tools/user-agent/',
     {userAgent: 'Chrome'});

   win.on('closed', () => {
     win = null
   });
}

You can set the User-Agent header in the main process using onBeforeSendHeaders:

import { session } from 'electron';

session.defaultSession.webRequest.onBeforeSendHeaders((details, callback) => {
  details.requestHeaders['User-Agent'] = 'SuperDuperAgent';
  callback({ cancel: false, requestHeaders: details.requestHeaders });
});

Before loading file, you can call BrowserWindowInstance.webContents.setUserAgent()

mainWindow.webContents.setUserAgent(mainWindow.webContents.getUserAgent() + " Custom Value");
mainWindow.loadFile('renderer/index.html');

Works with electron 3.0.4 Previous solutions didn't work for me.

---

Electron 8.2.5 Update

In newer versions, setUserAgent method will be deprecated. Instead, use this;

mainWindow.webContents.userAgent //to get
mainWindow.webContents.userAgent = "Something" //to set

Just use this if you're using a <webview> tag, this works better for me

<webview src="https://www.github.com/" useragent="Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; AS; rv:11.0) like Gecko"></webview>