Razor Pages and Blazor are both web application frameworks developed by Microsoft. While they have some similarities, there are also some important differences between the two.

Razor Pages is a framework for building web applications that is based on the ASP.NET Core framework. It is focused on server-side rendering and follows the Model-View-Controller (MVC) pattern. With Razor Pages, you create pages that contain both the HTML markup and the server-side C# code that processes user requests and generates the dynamic content. Razor Pages makes it easy to create simple, lightweight web applications that use server-side rendering and traditional web forms.

On the other hand, Blazor is a relatively new framework that allows you to build web applications using C# and the .NET framework. It uses a combination of web technologies and libraries, including WebAssembly, to run .NET code directly in the browser. Blazor allows you to create full-fledged, interactive web applications using C# and the .NET framework, without needing to write any JavaScript. Since Blazor runs on the client-side, it provides a more interactive and responsive user interface.

One key difference between Razor Pages and Blazor is their approach to client-side interactivity. With Razor Pages, the server is responsible for rendering the HTML and processing user interactions, while with Blazor, everything happens on the client-side. Blazor uses a component-based architecture, where components are reusable UI elements that can be composed together to build complex web applications.

Another difference is the level of maturity and adoption. Razor Pages has been around for a while and is widely used by developers. It is well-documented and has a large ecosystem of libraries and tools. On the other hand, Blazor is relatively new and is still in the experimental phase. While it shows a lot of promise, it may not be suitable for all types of web applications, especially those that require intensive client-side interactivity or have strict performance requirements.

In summary, Razor Pages and Blazor are two different frameworks that have different goals and use cases. Razor Pages is a framework for building server-side rendered web applications, while Blazor is a framework for building client-side interactive web applications using C# and the .NET framework. Your choice between the two will depend on your specific requirements and preferences.