What Is Blazor? Full-Stack Web Apps in C#

What if you could build modern, interactive web apps — buttons that respond, forms that validate, pages that update — without writing JavaScript? That is the promise of Blazor, a web framework that lets you build full-stack apps in C#. And here's a fun fact we'll get to in a minute: the very page you are reading runs on it.

The big idea: one language, front to back

For most of the web's history, the deal was simple: whatever language you used on the server, the browser only spoke JavaScript. So teams wrote their backend in one language and their frontend in another, then spent real effort keeping the two in sync.

Blazor changes the deal. You write your UI in C#, and you can share the same models, validation rules, and helper code between client and server. One language, one set of skills, one mental model — which is a big win if you are already learning C# first.

Components: the LEGO bricks of Blazor

Everything in Blazor is a component: a self-contained piece of UI that bundles its markup and its logic together in one file. Here is the classic counter component:

@page "/counter"

<h3>Counter</h3>

<p>Current count: @currentCount</p>

<button @onclick="IncrementCount">Click me</button>

@code {
    private int currentCount = 0;

    private void IncrementCount()
    {
        currentCount++;
    }
}

Read it top to bottom: some familiar HTML, a button wired to a C# method with @onclick, and the logic sitting right below in a @code block. The @ symbol is Razor syntax — it weaves C# into your HTML. Click the button, the count goes up, the page updates. No JavaScript in sight.

Components snap together like LEGO bricks: a page is a component, made of smaller components, which might contain even smaller ones. Build a nice button or card once, reuse it everywhere.

The three ways Blazor runs

Here is where beginners often get confused, so let's keep it plain. Blazor is one framework with three ways of running your components:

Even better, you can mix these in a single app: render most pages as static HTML and turn on interactivity only for the components that need it.

When Blazor is a great fit

• You know (or are learning) C#. You get a full-stack web career path without learning a second ecosystem first.
• Business apps and dashboards. Forms, tables, validation, authentication — Blazor and the .NET ecosystem handle these beautifully.
• Shared logic. When client and server must agree on rules (say, order validation), writing them once in C# removes a whole class of bugs.

And when do JavaScript frameworks make sense? Honestly, often: if your team already lives in JavaScript or TypeScript, or your project leans on the enormous JS ecosystem of UI libraries, React, Vue, and friends are excellent choices. Blazor's pitch isn't "JavaScript is bad" — it's "C# developers shouldn't need a second language to ship a web app."

Try it yourself

One command scaffolds a working app you can explore:

dotnet new blazor -n MyFirstBlazorApp
cd MyFirstBlazorApp
dotnet run

Open the address it prints, click around, then open the Counter page's file and change something. Watching your C# edit show up in the browser is a genuinely great moment.

You now know more about Blazor's moving parts than many working developers. For the magic that lets C# run inside a browser, read What Is WebAssembly? — and if you're still deciding on a first language, here's the case for C#. See you in the next one!