Use fetchpriority to hint resource loading priority

Browsers use internal heuristics to guess resource priority, but they cannot know which image is your LCP candidate. Adding fetchpriority="high" to the LCP image has been shown to reduce LCP by 5–30 % in real-world tests, directly improving Core Web Vitals scores and user-perceived load speed. The attribute costs nothing to add and is the lowest-effort high-impact performance optimisation available today.

Quick Reference

• Add fetchpriority="high" to the LCP image to accelerate Largest Contentful Paint
• Add fetchpriority="low" to below-the-fold images that would otherwise compete with critical resources
• Use fetchpriority="high" on for critical fonts and CSS
• Avoid marking more than one or two resources as high priority — it defeats the purpose

Check

Check whether the LCP image or hero element has fetchpriority="high" and whether any high-priority preload links are missing the attribute.

Fix

Add fetchpriority="high" to the LCP image element and any preloaded critical resources, and fetchpriority="low" to non-critical below-the-fold images.

Explain

Explain how the browser's resource priority queue works and how fetchpriority hints change loading order to improve LCP.

Code Review

Review the HTML for images above the fold. Flag the LCP candidate if it lacks fetchpriority="high", and flag any carousel or below-fold images that lack fetchpriority="low" (they compete with critical resources).

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For full implementation details, code examples, and framework-specific guidance, see references/rule.md.

Rule page: https://frontendchecklist.io/en/rules/performance/fetchpriority-attribute