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CSS File Size Audit

Audits CSS file size and suggests minifying, removing unused styles, and splitting stylesheets, after verifying the bottleneck.

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

What it does

When installed, this skill tells an AI agent to review a website's stylesheets for performance problems caused by large CSS files, which can delay how quickly a page starts showing content. The agent is instructed to check file sizes against a rough guideline (for example, over 50KB gzipped), confirm the real bottleneck with tools like browser DevTools, Lighthouse, or field data before recommending changes, and then suggest fixes such as minifying CSS, removing unused styles, or splitting large stylesheets into page-specific files.

Great for

  • Front-end developers trying to speed up a slow-loading website
  • Teams preparing a performance review of a site's stylesheets
  • Anyone who wants a structured checklist-style CSS performance audit from an AI agent

Skip it if

  • Projects where the main slowdown is images, JavaScript, or server response time, since this skill only covers CSS size (it does not measure those)
  • Situations where the agent is expected to apply changes without a human reviewing them, since the skill recommends measuring first and changes to live stylesheets can break page layout

Try asking

  • “Audit the CSS files in this project for size problems that could slow down page rendering”
  • “Check whether our stylesheets are too large and suggest which unused rules to remove”
  • “Review our site's CSS loading behavior and recommend how to split it into smaller files”
Step-by-step guide: how to use CSS File Size AuditInstall, 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-file-size.zip
  2. 2

    Add it to your agent

    Claude Code (all projects)

    mkdir -p ~/.claude/skills && unzip css-file-size.zip -d ~/.claude/skills/

    Claude Code / Agent SDK (this project only)

    mkdir -p .claude/skills && unzip css-file-size.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 real measurements from DevTools, Lighthouse, or your analytics so it can confirm CSS is actually the bottleneck.
  • Ask for the specific files and rules it flags, then review removals of unused CSS before deploying, since tools like PurgeCSS can remove styles still needed for dynamic content.
  • Point the agent at references/rule.md if you want framework-specific implementation details.

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.