Chrome field data reports poor Cumulative Layout Shift
ShipReady received origin-level Chrome UX Report field data with a CLS 75th percentile above 0.25.
Why it matters
A high field CLS value indicates that a substantial share of observed Chrome visits experienced visual instability while pages loaded.
How ShipReady detects it
What it inspects
ShipReady sends one request to the Chrome UX Report API for the scanned origin and reads the cumulative_layout_shift p75 and its open-ended poor histogram bucket.
What triggers a finding
The rule triggers only when CrUX returns a CLS p75 strictly greater than 0.25. Values at the threshold and the middle band are not reported.
What the evidence shows
Google's origin-level Chrome field dataset reported the displayed CLS p75 and poor-bucket share for the trailing field-data window.
Limits of this check
This is origin-level field data, not a page trace. ShipReady does not render the page, identify shifting elements, infer the cause, or guarantee coverage for low-traffic origins. Missing API configuration, unavailable data, and absent metrics do not create a finding.
How to fix it
Investigate with page-level layout tools
Use browser tooling and representative viewports to identify actual shifting elements before choosing a fix.
How to verify the change
Validate stability after deployment
Recheck origin field data after sufficient traffic and use controlled page-level traces to confirm the intended layout behavior.
Expected: The origin-level CLS p75 moves out of the poor band.