Rendering Content Visibility

---
name: rendering-content-visibility
description: CSS content-visibility for Long Lists. Use when you need help with rendering content visibility.
license: CC-BY-NC-SA-4.0
metadata:
  risk: unknown
  source: community
  kind: mode
  category: rules
---

## 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).