Blazor WebAssembly is a free, open-source web framework from Microsoft that lets you build interactive web applications using C# and .NET instead of JavaScript. It runs entirely in the browser using WebAssembly — a binary instruction format that modern browsers execute at near-native speed.
Why Blazor WASM
- Write client-side UI logic in C# — no JavaScript required
- Share code between client and server: models, validation, business logic
- Leverage the full .NET ecosystem: NuGet packages, C# features, type safety
- Deploy as static files — no server needed at runtime
- Works offline after first load (PWA-capable)
How It Works
When the user visits your app, the browser downloads the .NET runtime and your compiled app as WebAssembly binaries. After that, your C# code executes directly in the browser sandbox — no plugins, no extensions.
Blazor WASM vs Blazor Server
- Blazor WASM — runs in browser, works offline, no persistent server connection
- Blazor Server — runs on server, UI updates via SignalR, smaller download, requires connection
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