field-web-performance
Field Web Performance
A Lighthouse score is a thermometer, not a backlog. Field data (CrUX or your own RUM, at the 75th percentile) says what visitors experience. Observed traces say why. A simulated lab score is a model's projection of one fast trace onto a slow phone, and it can be off by more than an order of magnitude in either direction. Treat it as a signal to investigate, never as a list of work.
In one audit, the simulated LCP on the home page was 11,059 ms against a 6,000 ms budget. The observed LCP in the same run was 531 ms. Neither number described real visitors, and the team nearly spent weeks trimming bundles to move the first one.
The point of this skill is to make every performance claim traceable to the right kind of number, and to stop work that cannot move the metric that matters.