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Non-Blocking CSS Loading

Review and fix CSS loading so stylesheets don't delay the first paint of a page

Source Download skill
Repository
thedaviddias/Front-End-Checklist
Stars
74,632
Licence
MIT
Files
2 files

What it does

Once installed, the agent reviews how a site loads its stylesheets and checks whether they delay the first time a page appears on screen. It can suggest fixes such as preloading styles, inlining critical CSS, or splitting styles by media query, and then check the rendered layout across screen sizes and interaction states. The skill is a short checklist plus a link to a longer reference guide.

Great for

  • Front-end developers who want to speed up a slow-loading site
  • Teams reviewing performance before a release
  • Anyone who wants a structured checklist for render-blocking CSS

Skip it if

  • Projects that already use a framework like Next.js or Vite, where the framework often handles this automatically (the skill itself notes this), so the advice may be redundant
  • Non-developers without access to the site's code, since the skill needs source files to review
  • Making changes to production styles without testing, because preloading or deferring CSS can cause a flash of unstyled content or broken layouts

Try asking

  • “Review my index.html and stylesheets for render-blocking CSS and suggest a fix”
  • “Explain why my page shows a blank screen while the CSS downloads”
  • “Propose a non-blocking loading approach for my critical styles and check the mobile layout afterwards”
Step-by-step guide: how to use Non-Blocking CSS LoadingInstall, first run, examples, tips and FAQs

Install in 3 steps

  1. 1

    Download the skill

    The ZIP contains the 2 original files, the MIT licence and an attribution note.

    css-non-blocking.zip
  2. 2

    Add it to your agent

    Claude Code (all projects)

    mkdir -p ~/.claude/skills && unzip css-non-blocking.zip -d ~/.claude/skills/

    Claude Code / Agent SDK (this project only)

    mkdir -p .claude/skills && unzip css-non-blocking.zip -d .claude/skills/

    Claude apps (web/desktop): Settings → Capabilities → Skills → Upload skill, and choose the ZIP.

  3. 3

    Ask for the task

    No special command needed — the agent reads the skill's description and loads it when your request matches. Try one of the prompts above.

Get better results

  • Give the agent your actual HTML head and stylesheet files so it can flag exact selectors or breakpoints rather than generic advice.
  • Test any suggested change across breakpoints, because deferred CSS can cause layout shifts.
  • Check the referenced rule page for framework-specific examples before applying the loadCSS polyfill approach.

What's inside

  • references/rule.md
  • SKILL.md

Redistributed unmodified from thedaviddias/Front-End-Checklist under the MIT licence. The assessment was drafted with AI from the skill's files on 2026-10-29. Skills can instruct your agent to run code — read SKILL.md and any scripts before installing.