React Performance: Rendering — Content Visibility. Keywords: content-visibility auto. Platform: React/Next.js. Description: Apply content-visibility: auto to defer off-screen rendering. Do: Use content-visibility for long lists. Don't: Render all list items immediately. Good Example: .item { content-visibility: auto; contain-intrinsic-size: 0 80px }. Bad Example: Render 1000 items without optimization. Severity: High.