Import this at the top of /pages/_app.js in your Next.js app

analytics.js

import Router from 'next/router';
import Analytics from 'analytics';
import googleAnalyticsPlugin from 'analytics-plugin-ga';

const analytics = Analytics({
  debug: process.env.NODE_ENV !== 'production',
  plugins: [
    googleAnalyticsPlugin({
      trackingId: process.env.GA_TRACKING_ID
    })
  ]
});

if (typeof window !== 'undefined') {
  analytics.page();
}

Router.onRouteChangeComplete = url => {
  analytics.page();
};