In App Browser

import { InAppBrowser } from '@ionic-native/in-app-browser';

constructor(private iab: InAppBrowser) { }


...


const browser = this.iab.create('https://ionicframework.com/');

browser.executeScript(...);

browser.insertCSS(...);
browser.on('loadstop').subscribe(event => {
   browser.insertCSS({ code: "body{color: red;" });
});

browser.close();