SKILL.md
Core Web Vitals optimization
Targeted optimization for the three Core Web Vitals using field data to identify user impact and browser traces to diagnose causes.
Measure before optimizing
When a runnable URL is available, read the performance measurement workflow. Prefer this sequence:
- Check page-level CrUX p75 data, with a clearly labeled origin fallback when page data is unavailable.
- Record a browser performance trace under stated conditions. With Chrome DevTools MCP, trace summaries can include CrUX alongside the observed lab metrics.
- Analyze only the insights associated with the failing metric, then inspect the implicated code and resources.
- Re-run equivalent lab measurements after the fix. Do not claim an immediate field improvement; CrUX and first-party RUM need new user visits.
If only source code is available, identify likely causes but do not claim that LCP, INP, or CLS is failing without runtime evidence.