Loading skill
Install any skill in seconds. Free to start, no credit card required.
Get Started Free →Use when reviewing image assets, markup, and CDN or build transforms related to Use WebP format with fallbacks. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.
| Test case | Without → With | Effect | Δ tokens | Δ turns |
|---|---|---|---|---|
| case-01 | ✗→✓ | ▲ Improved | -14% | 0% |
| case-03 | ✗→✓ | ▲ Improved | -30% | 0% |
| case-12 | ✗→✓ | ▲ Improved | -29% | 0% |
| case-04 | ✓→✓ | ＝ Same ✓ | 25% | 0% |
| case-05 | ✓→✓ | ＝ Same ✓ | -39% | 0% |
WebP is smaller than JPEG and PNG at similar quality—using it reduces page weight by 25-35% for images, improving load times on all devices.
Check if images are served in modern formats like WebP with fallbacks for older browsers.
Convert images to WebP format and implement proper fallback strategies.
Explain how WebP provides 25-35% better compression than JPEG and PNG.
Review image assets, markup, and delivery configuration related to Use WebP format with fallbacks. Flag exact files or components where format choice, sizing, or loading behavior violates the rule, and describe how to confirm the fix in DevTools.
For full implementation details, code examples, and framework-specific guidance, see references/rule.md.
Rule page: https://frontendchecklist.io/en/rules/images/webp-format
Other measured skills in the registry, with their headline benchmark lift.