Retrieve the CSS stored in the browser's memory

cssdump.js

(async () => {
  let css = '';

  for (const sheet of document.styleSheets) {
    try {
      for (const rule of sheet.cssRules) {
        css += rule.cssText + '\n';
      }
    } catch (e) {
      console.warn('Blocked:', sheet.href);
    }
  }

  console.log(css);
})();