calendar/agents/skills/vercel-react-best-practices/rules/rendering-content-visibility.md

title, impact, impactDescription, tags

title	impact	impactDescription	tags
CSS content-visibility for Long Lists	HIGH	faster initial render	rendering, css, content-visibility, long-lists

CSS content-visibility for Long Lists

Apply content-visibility: auto to defer off-screen rendering.

CSS:

.message-item {
  content-visibility: auto;
  contain-intrinsic-size: 0 80px;
}

Example:

function MessageList({ messages }: { messages: Message[] }) {
  return (
    <div className="overflow-y-auto h-screen">
      {messages.map(msg => (
        <div key={msg.id} className="message-item">
          <Avatar user={msg.author} />
          <div>{msg.content}</div>
        </div>
      ))}
    </div>
  )
}

For 1000 messages, browser skips layout/paint for ~990 off-screen items (10× faster initial render).