I hate slow websites. They are annoying to use and frustrating to work on. But what does it mean to be “slow”? It used to be waiting for document load. Then waiting for page ready. But with so many asynchronous patterns in use today, how do we even define what “slow” is?
The W3C has been working on this with the new Event Timing and Element Timing API, and has defined some new Web Vital metrics to describe the different ways that slow performance can impact a webpage. Google is even going to use these web vital metrics as a search ranking factor!
Let’s have a look at them, and how we can apply them to keep our site fast and our pages well-ranked.
1. Largest Contentful Paint (LCP)
Some websites look like they loaded fast, but all the meaningful content is still waiting to be loaded.