Visually Complete and Speed Index have been introduced to better measure real end user performance experience. Klaus Enzenhofer @kenzenhofer ( https://twitter.com/kenzenhofer ) gives us a detailed description of these metrics, how they are getting calculated, and which problem they solve. What we also learn in this 101 is why now we finally have these metrics available not just for synthetic monitoring but also for real user monitoring. This can be attributed to the advances in browser technologies as well as to some smart engineering. In our discussion we also cover other recent advances and use cases in Web Performance Optimization – such as the usage of performance markers.If you want to learn more check out the blogs from Google on Speed Index ( https://sites.google.com/a/webpagetest.org/docs/using-webpagetest/metrics/speed-index ) as well as the blog from Klaus on how Speed Index and Visually Complete made it into RUM offerings ( https://www.dynatrace.com/blog/visually-complete-speed-index-for-real-user-monitoring-rum/ ).