1. Key difference 1: Performance: One of the key differences between ASP.NET Core and Blazor is the performance. ASP.NET Core is a server-side framework that processes requests on the server and sends the rendered HTML to the client. On the other hand, Blazor is a client-side framework that runs on the client's web browser using WebAssembly. This allows Blazor to execute code directly on the client, resulting in faster load times and improved performance.

2. Key difference 2: Language: Another significant difference between ASP.NET Core and Blazor is the programming language used. ASP.NET Core primarily uses C# for server-side development. In contrast, Blazor allows developers to write client-side web applications using C# and Razor syntax, eliminating the need to use JavaScript. This makes it easier for developers who are already familiar with C# to build full-stack web applications.

3. Key difference 3: User Interface: ASP.NET Core is focused on server-side rendering, where the HTML is generated on the server and sent to the client. In contrast, Blazor utilizes a component-based approach for building user interfaces, similar to modern JavaScript frameworks like React or Angular. With Blazor, developers can create reusable UI components that are rendered on the client-side, enhancing the interactivity and responsiveness of the application.

4. Key difference 4: Framework Size: ASP.NET Core is a lightweight framework that offers only the essential components for building web applications. This minimalistic approach results in a smaller framework size, faster startup times, and efficient resource usage. On the other hand, Blazor includes the complete .NET runtime required for executing C# code on the client-side, leading to a larger framework size and potentially longer load times.

5. Key difference 5: Development Workflow: ASP.NET Core follows a traditional server-side development workflow, where developers write code, compile it, and then deploy the application to a server. Blazor, being a client-side framework, allows for a more streamlined development workflow. Developers can write and test the code directly in the browser, without requiring a separate compilation and deployment step. This enables faster iteration and prototyping during the development process.

6. Key difference 6: Cross-platform and Mobile Capabilities: ASP.NET Core is known for its cross-platform capabilities, allowing developers to build web applications that can run on Windows, Linux, and macOS. However, when it comes to mobile application development, Blazor has the upper hand. Blazor offers the ability to build native mobile applications using frameworks like Xamarin, leveraging the power of C# and the .NET ecosystem for mobile development.

In Summary, ASP.NET Core is a server-side framework focused on performance and traditional development workflow, while Blazor is a client-side framework that leverages WebAssembly and offers a component-based approach for building user interfaces. Blazor also provides the advantage of using C# for both client-side and mobile application development.