core-web-vitalslisted

# Core Web Vitals Two things to get straight before doing any work. **Field data is the only data that counts.** Google ranks on CrUX, which is real Chrome users on real devices and networks. Lighthouse is a simulated lab run on your machine. It's a debugging tool, not a scoreboard. A Lighthouse score of 100 and a failing field LCP happen together constantly. **The ranking effect is small.** Page experience is a minor signal and Google has said as much. Fix these because a slow page loses users and conversions, which is a much bigger number than the ranking delta. If someone is choosing between fixing LCP and fixing content, fix the content. ## The thresholds | Metric | Good | Needs work | Poor | What it measures | |---|---|---|---|---| | **LCP** | ≤ 2.5s | ≤ 4.0s | > 4.0s | When the main content appears | | **INP** | ≤ 200ms | ≤ 500ms | > 500ms | How fast the page responds to interaction | | **CLS** | ≤ 0.1 | ≤ 0.25 | > 0.25 | How much the layout jumps | Scored at the **75th percentile** of real users. Meaning a quarter of your visitors can be having a bad time while the metric passes. Look at the distribution, not just the pass or fail. ## Step 1: Get the field data ```bash curl -s "https://www.googleapis.com/pagespeedonline/v5/runPagespeed?url=https://example.com&strategy=mobile&key=$PSI_KEY" \ | python -c " import sys, json d = json.load(sys.stdin).get('loadingExperience', {}).get('metrics', {}) for k, v in d.items(): print(f\"{k:42} {v['percentile']:>7} {v[