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CSS Containment Review

Reviews stylesheets to find components that can use CSS containment to limit repaint and layout work

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

What it does

Once installed, the agent looks at your CSS and component styles and checks whether self-contained parts of the page could be marked with CSS containment (contain: layout style paint, or content-visibility: auto for long off-screen lists). It explains what each value does, proposes the change, and flags selectors or breakpoints that conflict with the rule. It is guidance for a human developer, not a tool that changes the site on its own.

Great for

  • Front-end developers trying to speed up pages with many independent components
  • Teams doing performance reviews of long lists or dashboards
  • Developers learning what CSS containment does and when it is safe

Skip it if

  • Projects whose components overflow or affect elements outside them, since contain values can clip content or change layout (the skill itself warns to use strict only for widgets with no overflow)
  • Simple static sites where rendering performance is not a concern, since the change adds complexity for little gain

Try asking

  • “Review my component stylesheets and tell me which components could use contain: layout style paint”
  • “Check this product list CSS and suggest where content-visibility: auto would help off-screen items”
  • “Explain what contain: strict would do to this card widget before I add it”
Step-by-step guide: how to use CSS Containment ReviewInstall, 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-containment.zip
  2. 2

    Add it to your agent

    Claude Code (all projects)

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

    Claude Code / Agent SDK (this project only)

    mkdir -p .claude/skills && unzip css-containment.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 the actual stylesheet or component files plus the breakpoints you care about, so its suggestions are grounded in your code.
  • Test each suggested containment change in the browser across breakpoints and interaction states before shipping, because clipping or layout shifts are easy to miss.
  • Ask for an explanation of each value first if you are new to containment, then decide which ones to apply.

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.