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Slow main content (LCP)

performance.cwv_lcp_poor
Priority
Medium
Severity
Critical

What we look for

In Google's PageSpeed Insights test (one lab load of each page), these pages took more than 4 seconds to show their largest image or text block, a measure called LCP (Largest Contentful Paint).

Why it matters

LCP is one of Google's Core Web Vitals (page experience scores), and this is rated Poor. Visitors looking at a half-loaded page often leave.

How to fix

Make the largest element load sooner: compress and resize the main image, serve it in a modern format such as WebP, and remove scripts and styles that hold up drawing. A faster server response helps too.

What it cannot know

This is one lab load per page, run on Google's servers. Real visitors' times can differ.

Where you’ll see it

The id is stable, and every surface uses it, so it’s the thing to search for or hand to an agent.

Terminal
When it is one of the five findings under Fix first, raptor crawl prints the id under it.
Check: performance.cwv_lcp_poor
crawl.json and the CSV
The crawl JSON names the finding by this id, and so do the CSV and raptor_query.
"check_id": "performance.cwv_lcp_poor"
The HTML report
This link opens the finding in the report, and each finding shows its id.
crawl.html#finding=performance.cwv_lcp_poor
MCP
raptor_findings with this check_id returns the finding in full, with a fix brief ready to paste into a task. If it didn’t fire, it says why.
raptor_findings {
  "job_id": "...",
  "check_id": "performance.cwv_lcp_poor"
}