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CLS by HTTP status code

CLS by HTTP status code without noise

Vasil Dachev avatar
Written by Vasil Dachev
Updated over a week ago


What is CLS by HTTP status code

CLS by HTTP status code shows how Cumulative Layout Shift (CLS) varies based on the HTTP status returned by your server — such as 200 (OK), 301 (redirect), 404 (not found), or 500 (server error).

This lens helps identify whether non-200 responses are introducing layout instability, such as shifts in fallback templates, error pages, or redirect chains that result in unexpected reflows or content jumps.

Healthy CLS by HTTP status code sample

A healthy lens shows:

  • Low CLS on 200 status pages, with green bars dominating the chart

  • Occasional 3xx or 4xx responses that don’t trigger layout shifts

  • Clean fallback pages that don’t introduce jarring reflows

This indicates that your layout remains stable even when users land on error states or are redirected — a mark of solid UX and consistent styling.

Unhealthy CLS by HTTP status code sample

An unhealthy breakdown often reveals:

  • Redirect loops or unstyled redirects (301, 302) causing flash-of-unstyled-content (FOUC) or reflows

  • 404 or 500 pages loading without proper placeholders, shifting as fonts, scripts, or assets catch up

  • Fallback templates that render with dynamic height changes or late layout injections

These shifts degrade user trust and usability — especially when they occur during confusion, like a missing page or login failure.

Resolving unhealthy CLS by HTTP status code

Go-to action plan to resolve an unhealthy CLS by HTTP status code:

  1. Ask Uxi to analyze your CLS by HTTP status code values and suggest improvements

  2. Use Filters to isolate routes with high CLS on 3xx, 4xx, or 5xx statuses.

  3. Simulate CLS of the suspected lens to see if fixing it will resolve the CLS by HTTP status code. If yes, this is where the resolution focus should be.

  4. Use an automated CLS optimization tool like Navigation AI to improve your CLS by HTTP status code values

  5. Once you’ve improved CLS, set an alert to be the first to know if it starts worsening again.

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