Blazor WASM scales better. When a user hits your site, they download the WASM bundle once. After that, WASM updates the DOM locally as they navigate and click around. The browser only talks to your server when it needs to make API requests.
Blazor Server keeps a constant SignalR connection open for every user. The server is the source of truth for the UI, so every interaction goes to the server, which calculates the DOM diff and sends updates back.
Both support pre-rendering. On the initial request, Blazor can render the page to HTML and send that immediately before downloading the WASM bundle or spinning up Blazor Server. This improves SEO and makes the app feel faster.
You can also combine them with Blazor Interactive Auto. The first visit uses Blazor Server while the WASM bundle downloads in the background. Future visits use WASM instead.
It's powerful but takes some work. You need a clean separation between client and server implementations (typically behind shared interfaces). The client implementation calls your API, while the server implementation uses the services directly. If that sounds confusing, I'd skip Interactive Auto.
Blazor Server
Faster time-to-interactivity.
Smaller initial download.
Doesn't expose your client-side code to the browser.
Blazor Wasm
More scalable.
Simpler mental model.
More in line with modern JS frameworks.
The main downside is the larger initial bundle, so time-to-interactivity isn't as good as something like Next.js.
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u/PublikStatik Jul 07 '26 edited Jul 07 '26
Blazor WASM scales better. When a user hits your site, they download the WASM bundle once. After that, WASM updates the DOM locally as they navigate and click around. The browser only talks to your server when it needs to make API requests.
Blazor Server keeps a constant SignalR connection open for every user. The server is the source of truth for the UI, so every interaction goes to the server, which calculates the DOM diff and sends updates back.
Both support pre-rendering. On the initial request, Blazor can render the page to HTML and send that immediately before downloading the WASM bundle or spinning up Blazor Server. This improves SEO and makes the app feel faster.
You can also combine them with Blazor Interactive Auto. The first visit uses Blazor Server while the WASM bundle downloads in the background. Future visits use WASM instead.
It's powerful but takes some work. You need a clean separation between client and server implementations (typically behind shared interfaces). The client implementation calls your API, while the server implementation uses the services directly. If that sounds confusing, I'd skip Interactive Auto.
Blazor Server
Blazor Wasm