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Critical Images

Testing & Quality
critical-images

Critical Images is an Agent Skill for testing & quality published in the thedaviddias/Front-End-Checklist repository on GitHub: a SKILL.md instruction file an AI agent can load to do this task.

Use when reviewing image assets, markup, and CDN or build transforms related to Prioritize loading critical images. Check encoded size, rendered size, loading strategy, and above-the-fold impact together.

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How to use this skill

Bring this guide into your coding agent with a prompt tailored to the tool you use.

  1. Open your project in Codex.
  2. Copy and paste the prompt below.
  3. Review files and risks before approving any action.
Prompt to paste
Inspect the Agent Skill at https://github.com/thedaviddias/Front-End-Checklist/blob/HEAD/skills/critical-images/SKILL.md and all supporting files. Report provenance, permissions, scripts, dependencies, and security risks. Propose an exact installation into .agents/skills/critical-images, but wait for my approval before writing files or running scripts.

Copying this prompt does not install or run the skill. Review third-party files before use.

Prioritize loading critical images

The Largest Contentful Paint (LCP) is often an image—prioritizing its load can improve LCP by 20-40%, directly impacting Core Web Vitals and SEO.

Quick Reference

  • Use fetchpriority='high' on LCP images
  • Preload hero images in document head
  • Remove loading='lazy' from above-the-fold images
  • Critical images directly impact LCP Core Web Vital

Check

Identify which images are critical for initial render and ensure they load with high priority.

Fix

Add fetchpriority='high' to critical images and use preload for hero images.

Explain

Explain how prioritizing critical images improves Largest Contentful Paint (LCP).

Code Review

Review image assets, markup, and delivery configuration related to Prioritize loading critical images. 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/critical-images