Declare image width and height or aspect-ratio in HTML.
- Declare image width and height or aspect-ratio in HTML7 cited sources5 categories
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Why this matters
Specifying dimensions prevents layout shifts and improves user experience signals like CLS (Cumulative Layout Shift).
Hypothetical standard operating procedure
Adapt this example to your site, access, tools, and change process. It is our suggested procedure, informed by the sources below.
- Audit images missing width and height attributes.
- Update image tags to include accurate pixel dimensions or CSS aspect-ratios.
- Test pages for layout shifts before and after implementation.
- Verify metrics improvements in Core Web Vitals reports.
- Incorporate dimensions check into content publishing workflows.
Watch for
Missing width/height leads to layout jumps as images load, hurting Core Web Vitals and user trust.
Definition of done
All images have explicit width and height or CSS aspect-ratio to reserve space before loading.
Sources & attribution
Original checklist wording and example SOP by Best SEO Checklist, using source-grounded AI assistance. Editorial contact: Ted Kubaitis, @tedkubaitis on Teams. Check current source guidance before implementation.