Performance is part of the experience.
A page can look considered and still feel frustrating. Maybe its main image arrives late. Maybe a button moves just as someone tries to press it. Maybe an animation keeps a phone busy.
Core Web Vitals describe three parts of that experience: loading through Largest Contentful Paint, responsiveness through Interaction to Next Paint, and visual stability through Cumulative Layout Shift.
Give the first view priority.
Make the essential content available early. Size images for their purpose. Keep the first load focused, and load optional interactive experiences when they are needed.
Leave space for what arrives later.
Declare image dimensions and reserve room for embeds. A page should remain understandable while resources load, rather than rearranging itself around the reader.
Test the journey, not just a score.
Try navigation, menus, and contact actions on a real phone. Review field data when you have it, and use lab tools to investigate the specific moments that feel slow.
See Google’s Web Vitals guide for the metrics and how to measure them.