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Get Started Free →Use when reviewing article images, cards, galleries, or any component rendered at multiple sizes across breakpoints. Check both the markup and the CSS layout because an incorrect `sizes` attribute can negate a perfectly good `srcset`.
| Test case | Without → With | Effect | Δ tokens | Δ turns |
|---|---|---|---|---|
| case-18 | ✗→✓ | ▲ Improved | -77% | 0% |
| case-20 | ✓→✗ | ▼ Worse | 36% | 0% |
| case-01 | ✓→✓ | ＝ Same ✓ | -4% | 0% |
| case-02 | ✓→✓ | ＝ Same ✓ | -9% | 0% |
| case-03 | ✓→✓ | ＝ Same ✓ | -12% | 0% |
Serving a 2000px image to a 400px phone screen wastes bandwidth and slows loading—srcset lets the browser download only the size it needs.
Verify that images use srcset and sizes attributes for responsive delivery.
Implement responsive images with srcset for different screen sizes and resolutions.
Explain how responsive images deliver optimized versions based on device capabilities.
Inspect image markup and component abstractions for srcset, sizes, and width/height handling. Flag pages that always ship desktop-sized assets to mobile, omit sizes, or generate variants that do not match the actual rendered layout.
For full implementation details, code examples, and framework-specific guidance, see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/images/responsive-images
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