Lazy loading reduces the initial download size of a Blazor WASM app by deferring non-essential assemblies until they are actually needed.

Why Lazy Load

• The default Blazor WASM download includes all referenced assemblies
• Large apps can have 5–20MB+ initial payloads
• Lazy loading ships a small shell that loads DLLs on demand

Configuration in .csproj

<ItemGroup>
  <BlazorWebAssemblyLazyLoad Include="MyApp.AdminFeatures.dll" />
</ItemGroup>

Loading Assemblies in App.razor

<Router AppAssembly="@typeof(App).Assembly"
        OnNavigateAsync="OnNavigateAsync">

@code {
    [Inject] private LazyAssemblyLoader AssemblyLoader { get; set; } = default!;

    private async Task OnNavigateAsync(NavigationContext context)
    {
        if (context.Path.StartsWith("admin"))
        {
            await AssemblyLoader.LoadAssembliesAsync(new[]
            {
                "MyApp.AdminFeatures.dll"
            });
        }
    }
}

Best Practice

Lazy load large, rarely-used features such as admin panels and reporting tools. Keep the core app shell small for fast first load.

Reference:

Wikipedia: Lazy Loading

https://en.wikipedia.org/wiki/Lazy_loading