The two halves of a report
| Compared | Lab data | Field data |
|---|---|---|
| Source | One simulated load | Real Chrome visitors |
| Time span | One moment | Last 28 days |
| Used by Google for ranking | No | Yes |
| Best for | Finding causes | Knowing if you pass |
Why they disagree on dealer sites
More on reading the whole report in PageSpeed scores for car dealers.
- The lab loads the page once and stops; real shoppers tap, scroll and swipe, which is where INP and layout shift show up.
- Real visitors use many phones and connections; the lab uses one.
- Field data covers four weeks, so a fix takes weeks to show fully.
Why a vehicle page often has no field data
Field data needs enough Chrome visits to one address over 28 days. A single vehicle page rarely gets that, because each car is only on the site for a few weeks. PageSpeed Insights then shows data for the whole site instead, labeled as origin data.
For a vehicle page, read the origin data for the pass-or-fail answer, and the lab test for what to fix on that template. Every vehicle page shares the template, so a fix on one reaches them all.