Blazor Web App vs Blazor Server App in .NET 8

Problem Statement

With the introduction of .NET 8, developers encounter a new project template called "Blazor Web App" alongside the existing "Blazor Server App." This causes confusion as both options seem to support server-side rendering of interactive components. The core challenge is understanding when to choose each template and whether the legacy Blazor Server approach is being deprecated.

Understanding the Templates

Blazor Server App (Legacy Template)

• Designed for .NET 7 and earlier versions
• Requires persistent SignalR connection (WebSocket by default)
• All UI interactions handled via round-trips to server
• Pros: Fast initial load, works on low-powered devices
• Cons:
  • Server resource intensive
  • Poor performance under high-latency networks
  • Disruptive user experience on connection loss
• Ideal for: Quick migration of MVC/Razor Pages apps

// Program.cs in Blazor Server App
builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();
app.MapBlazorHub();

Blazor Web App (.NET 8+ Template)

• Unified template merging server and WebAssembly capabilities
• Supports hybrid rendering modes per component/page:
  • Static SSR (non-interactive server rendering)
  • Interactive Server (via WebSockets)
  • Interactive WebAssembly (client-side execution)
  • Auto (starts with server, transitions to WASM)
• Key advantages:
  • Optimized server resource usage
  • Progressive enhancement capabilities
  • No upfront WASM download for SSR content
  • Modern .NET 8 features (streaming rendering, enhanced navigation)

// Program.cs in Blazor Web App
builder.Services.AddRazorComponents()
    .AddInteractiveServerComponents()   // Enable server interactivity
    .AddInteractiveWebAssemblyComponents(); // Optional: Add WASM support

app.MapRazorComponents<App>()
    .AddInteractiveServerRenderMode()   // Default render mode
    .AddInteractiveWebAssemblyRenderMode();

Key Differences Comparison

Feature	Blazor Server App	Blazor Web App
.NET Version Support	≤ 7.0	8.0+
Rendering Mode	Server-only	Hybrid/per-component
SignalR Requirement	Always required	Only for server interop
Project Structure	Monolithic	Component-based
WASM Integration	Not supported	Built-in support
Loading Strategy	Full page reloads	Streaming rendering
Code Protection	Server-side execution	Flexible per component

When to Choose Each Template

Blazor Web App Recommendations

1. New projects: Default choice for .NET 8+ development
2. Modern UI needs: Mix static content and interactive components
3. Scalability requirements: Offload computation to client via WASM
4. Optimized experiences: Use auto mode for best initial performance

Blazor Server App Limitations

• No longer recommended for new projects in .NET 8+
• Lacks modern rendering features like streaming/SSR
• Stateful architecture challenges cloud deployment

Migration and Compatibility

Existing Blazor Server apps:

• Continue working on .NET 8 without changes
• Can incrementally adopt new Blazor Web App features
• Migration path: Add new project and move components progressively

Conclusion

The new Blazor Web App template is the evolution of Blazor in .NET 8, superseding both legacy Blazor Server and WebAssembly templates. Key advantages include:

• Flexible render modes applied at component-level
• Hybrid server/client execution capabilities
• Support for static server-side rendering
• Optimized resource usage
• Future-proof architecture

For new development, always choose the Blazor Web App template to leverage the latest .NET capabilities. Existing Blazor Server apps remain supported but should adopt the new template incrementally to gain modern features.