The Evolution of React Rendering
React's rendering model has evolved dramatically: from client-side rendering (CSR) to server-side rendering (SSR) to the latest paradigm shift — React Server Components (RSC). But how do these approaches actually compare in real-world performance? We ran extensive benchmarks to find out.
Testing Methodology
We built identical applications using three approaches: traditional CSR with React, SSR with Next.js Pages Router, and RSC with Next.js App Router. Each application was a content-heavy dashboard with data fetching, filtering, and pagination. We tested on 3G, 4G, and broadband connections.
Key Metrics Compared
Time to First Byte (TTFB)
RSC showed a 35% improvement over traditional SSR due to streaming. Instead of waiting for all data to load before sending HTML, RSC streams components as they become ready. This means users see meaningful content faster, even when some data sources are slow.
Largest Contentful Paint (LCP)
RSC achieved an average LCP of 1.2 seconds compared to 1.8 seconds for traditional SSR and 3.1 seconds for CSR on 4G connections. The biggest win comes from eliminating client-side JavaScript for server components.
JavaScript Bundle Size
This is where RSC truly shines. Our RSC application shipped 62% less JavaScript to the client compared to the equivalent CSR application. Server Components don't include their code in the client bundle — only the rendered output is sent to the browser.
When to Use Each Approach
- RSC — Content-heavy applications, dashboards, e-commerce product pages
- Traditional SSR — Applications needing full control over the rendering pipeline
- CSR — Highly interactive applications like design tools or real-time collaboration
Conclusion
React Server Components represent a genuine performance improvement for most web applications. The reduced JavaScript bundle, streaming capability, and simplified data fetching make RSC the recommended approach for new Next.js projects in 2026.