# Render Blocking

> Use when auditing slow page loads, heavy assets, or rendering delays related to Eliminate render-blocking resources. Verify the actual bottleneck in DevTools, Lighthouse, or field data before recommending changes.

- Skill: `thedaviddias/render-blocking` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add thedaviddias/render-blocking`
- Raw SKILL.md: https://api.skillmd.com/api/skills/thedaviddias/render-blocking/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: thedaviddias (https://skillmd.com/u/thedaviddias)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/thedaviddias/render-blocking

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# Eliminate render-blocking resources

Render-blocking resources prevent the browser from painting anything on the screen, leading to a "white screen" effect and poor user experience.

## Quick Reference

- Load non-critical CSS and JS asynchronously using `defer`, `async`, or media queries
- Inline critical CSS to allow the page to start rendering immediately
- Avoid `@import` in CSS as it creates serial request chains

## Check

Review the page's resources and identify any CSS or JavaScript files that are blocking the initial render of the page.

## Fix

Update the loading strategy for render-blocking resources by using `defer`, `async`, or inlining critical styles.

## Explain

Explain how render-blocking resources impact the First Contentful Paint (FCP) and how to resolve them.

## Code Review

Review the routes, assets, and loading behavior that affect Eliminate render-blocking resources. Flag exact files, requests, or rendering steps that add unnecessary network, CPU, or layout cost, and describe the measurement method used to confirm the issue.

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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/render-blocking