Performance fix guide
Image Aspect Ratio Mismatch Causing Layout Shift
Images are rendered at different aspect ratios than their intrinsic dimensions, which can cause layout shifts and hurt CLS.
Issue ID: CWV-ASPECT-001
Severity: minor
Impact: Low
Effort: S
Use this article when
- You need deeper remediation guidance than the issue card can show.
- You want CMS-specific steps before handing the fix to a developer.
- You want a repeatable re-check path after shipping the change.
What this issue is
Images are rendered at different aspect ratios than their intrinsic dimensions, which can cause layout shifts and hurt CLS.
Why it matters
Images are rendered at different aspect ratios than their intrinsic dimensions, which can cause layout shifts and hurt CLS. This affects load speed, Core Web Vitals, and how many visitors stay long enough to convert.
How we detect it
- FreeSiteAudit flags this issue when the rule for CWV-ASPECT-001 fails and the page evidence points to Performance tool.
- You can usually confirm this by checking the page source or the relevant page settings inside your CMS.
Evidence examples
Check the affected page source, rendered output, or relevant CMS setting to confirm the missing or incorrect element.
How to fix it
- 1Set explicit width and height attributes on <img> elements
- 2Use CSS aspect-ratio property for responsive containers
- 3Avoid stretching or squishing images with CSS
How to re-check it
- Confirm CLS improvements after adding explicit dimensions
Related tools
This issue is best verified with the full FreeSiteAudit crawl rather than a single-point mini tool.