Blazor is a powerful framework from Microsoft used for building interactive web UIs with C# instead of JavaScript. A key feature of Blazor is its flexibility in how applications are hosted and run. The choice of hosting model—Server, WebAssembly, Interactive Auto, or Hybrid—depends entirely on the specific needs of the application, such as scale/performance requirements, offline capabilities, and access to native device features.

But which flavor of Blazor should you use? Well, that depends...

Blazor Server

The Blazor Server hosting model is the easiest to set up and use. It runs your application on the server, and when a user interacts with the application, UI events are sent to the server over a real-time (SignalR) connection. The server processes these events, calculates the necessary UI changes, and sends only those small changes back to the client to update the display. This results in a very thin client and a fast initial load time, as almost no application code is downloaded to the browser.

Best reasons to use this hosting model:

• internal business applications or other scenarios where a constant, low-latency connection to the server is guaranteed
• applications that need direct access to server-side resources, databases, or protected services that shouldn't be exposed to the client
• applications that don't have enterprise-scale traffic needs, or where the cost of hosting those resources is not prohibitive (e.g. regional instances for best performance)
• when the development cycle "inner loop" must be as fast and efficient as possible

Blazor WebAssembly (WASM)

In contrast, Blazor WebAssembly runs your entire application directly in the web browser using a WebAssembly-based .NET runtime. The application's C# code, its dependencies, and the .NET runtime itself, are all downloaded to the client. Once downloaded, the application executes entirely on the user's machine, enabling full offline functionality and leveraging the client's processing power for a rich, near-native user experience.

Best reasons to use this hosting model:

• for public-facing websites, progressive web apps (PWAs), and applications that require complex, desktop-like interactivity without constant server communication
• when a larger initial download size and longer first load time are not a concern
• when hosting cost is a concern; WebAssembly apps can be hosted on inexpensive file-based hosting platforms, like Amazon S3
• if your web application needs to support large amounts of traffic or will service an international audience
• when development cycle "inner loop" iteration time is not a concern

Blazor Interactive Auto

The Blazor interactive auto mode allows you to use both server and WebAssembly components in a single project, giving you precise control over how your app behaves.

Best reasons to use this hosting model:

• applications that are ideal for server hosting but also have some user experiences that need higher performance or support larger audiences
• when the complexity of configuring a WebAssembly project is not a concern
• when development cycle "inner loop" iteration time is not a concern

Blazor Hybrid

Blazor Hybrid is a bit different. It's not used for building web applications. It's allows web developers to use their skills to build mobile apps that run on devices at close to native speed. Microsoft Maui is the core platform, which is native and cross-platform. It normally uses XAML for coding user interfaces. When using Blazor Hybrid, however, you can also use Blazor web components alongside XAML or in place of it.

This model provides the best of both worlds: the ability to build a rich, cross-platform UI with web technologies while having full access to the native capabilities of the device, such as the file system, sensors, and notifications.

Blazor Hybrid is the perfect solution for developers looking to create desktop and mobile applications that can share UI components and logic with an existing Blazor web application, or for new mobile app projects.

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