CSS content-visibility for Long Lists

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

CSS:

css

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

Example:

tsx

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).