At a glance
Lab Performance Score over time, daily time-series of the Lighthouse Performance Score (0-100) on mobile profile. The deterministic engineering trend that pairs with field-data trends (crux_pass_rate_trend) for the full picture. Lab data updates in real-time after each audit run, while field data has a 28-day rolling lag. Use lab trend for: build-pipeline gating, post-deploy verification, engineering iteration. Use field trends for: ranking-impact decisions, monthly executive reporting.
Calculation
Calculated automatically from your Website Performance (PageSpeed + CrUX) data. See the At a glance summary above for what the metric tracks and the worked example below for a typical reading.Worked example
A UK-based BigCommerce fashion store, mobile lab score trend over 6 months ending Wednesday 15 May 26.
What the lab + field comparison is telling us:
- Lab trend leads field trend by 4-6 weeks. Each deploy / change shows up in lab within days; field absorbs over the 28-day rolling window. Reading lab and field trends together provides a leading-indicator + truth-source view.
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The Jan 26 6-point drop in lab was the early warning. Lab caught the regression ~28 days before field-CWV-pass-rate visibly dropped. A
+5 point lab score regressionalert would have fired then; investigating immediately would have prevented the cascade. - The Mar 26 8-point drop is the largest single-month regression. Two contributing changes (marketing stack + cache config) deployed in the same sprint window. CI/CD gating at “score must not drop > 5 points vs baseline” would have blocked at least one of these deploys, preventing the compound regression.
- Current 42 score is in red band (below 50). The optimisation cycle to recover to 70+ requires the work documented across the per-CWV cards: image optimisation, third-party deferral, render-blocking fix, cache restoration. Lab score is the primary build-gate metric; CI configuration update recommended to prevent recurrence.
- Lab vs field divergence is informative. When lab and field move together (this site’s pattern), real-user conditions roughly match emulation. When lab improves but field doesn’t, real users have slower devices/networks than emulation assumes; investigate audience profile.
- Compare lab trend with field trends. Lab leads; field confirms.
- Identify deploys / changes correlated with lab inflection points. Lab captures changes within 24-48 hours; cross-reference deploy log.
- Apply CI/CD gating to prevent regressions reaching production.
Sibling cards merchants should reference together
Reconciling against the vendor’s own dashboard
Where to look:- Lighthouse CI dashboard, historical lab scores from CI builds.
- PageSpeed Insights, current snapshot.
- Internal CI/CD logs, deploy-correlated score history.
Cross-connector reconciliation: primarily internal (with the field-data trend cards).
Quick rule for support tickets: if a merchant says “lab score dropped but field metrics didn’t move”, the field metrics will move 14-28 days later as the rolling window absorbs. Lab leads field by design.