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---
title: Introduction to .NET
description: Learn about .NET. .NET is a free, open-source development platform for building many kinds of apps.
ms.date: 1/5/2024
ms.date: 03/10/2026
ms.custom: "updateeachrelease"
ai-usage: ai-assisted
---
# Introduction to .NET

.NET is a free, cross-platform, [open-source developer platform](https://github.com/dotnet/core) for building [many kinds of applications](apps.md). It can run programs written in [multiple languages](../fundamentals/languages.md), with [C#](../csharp/index.yml) being the most popular. It relies on a [high-performance](https://devblogs.microsoft.com/dotnet/category/performance/) runtime that is used in production by many [high-scale apps](https://devblogs.microsoft.com/dotnet/category/developer-stories/).
.NET is a free, cross-platform, [open-source developer platform](https://github.com/dotnet/core) for building [many kinds of applications](apps.md). It can run programs written in [multiple languages](../fundamentals/languages.md), with [C#](../csharp/index.yml) being the most popular. It relies on a [high-performance](https://devblogs.microsoft.com/dotnet/category/performance/) runtime used in production by many [high-scale apps](https://devblogs.microsoft.com/dotnet/category/developer-stories/).

To learn how to [download .NET](https://dotnet.microsoft.com/download/) and start writing your first app, see [Getting started](./get-started.md).

The .NET platform has been designed to deliver productivity, performance, security, and reliability. It provides automatic memory management via a [garbage collector (GC)](../standard/automatic-memory-management.md). It is type-safe and memory-safe, due to using a GC and strict language compilers. It offers [concurrency](../csharp/asynchronous-programming/index.md) via `async`/`await` and `Task` primitives. It includes a large set of libraries that have broad functionality and have been optimized for performance on multiple operating systems and chip architectures.
The .NET platform is designed to deliver productivity, performance, security, and reliability. It provides automatic memory management via a [garbage collector (GC)](../standard/automatic-memory-management.md). It's type-safe and memory-safe, because it uses a GC and strict language compilers. It offers [concurrency](../csharp/asynchronous-programming/index.md) via `async`/`await` and `Task` primitives. It includes a large set of libraries that have broad functionality and that are optimized for performance on multiple operating systems and chip architectures.

.NET has the following [design points](https://devblogs.microsoft.com/dotnet/why-dotnet/):

* **Productivity is full-stack** with runtime, libraries, languages, and tools all contributing to developer user experience.
* **Safe code** is the primary compute model, while [unsafe code](../csharp/language-reference/unsafe-code.md) enables additional manual optimizations.
* **Safe code** is the primary compute model, while [unsafe code](../csharp/language-reference/unsafe-code.md) enables more manual optimizations.
* **Static and dynamic code** are both supported, enabling a broad set of distinct scenarios.
* **Native code interop and hardware intrinsics** are low cost and high-fidelity (raw API and instruction access).
* **Code is portable across platforms** (OS and chip architecture), while platform targeting enables specialization and optimization.
Expand All @@ -28,11 +29,11 @@ The .NET platform has been designed to deliver productivity, performance, securi

.NET includes the following components:

- Runtime -- executes application code.
- Libraries -- provides utility functionality like [JSON parsing](../standard/serialization/system-text-json/overview.md).
- Compiler -- compiles C# (and other languages) source code into (runtime) executable code.
- SDK and other tools -- enable building and monitoring apps with modern workflows.
- App stacks -- like ASP.NET Core and Windows Forms, that enable writing apps.
- Runtime — executes application code.
- Libraries — provide utility functionality like [JSON parsing](../standard/serialization/system-text-json/overview.md).
- Compiler — compiles C# (and other languages) source code into (runtime) executable code.
- SDK and other tools — enable building and monitoring apps with modern workflows.
- App stacks — like ASP.NET Core and Windows Forms that enable writing apps.

The runtime, libraries, and languages are the pillars of the .NET stack. Higher-level components, like .NET tools, and app stacks, like ASP.NET Core, build on top of these pillars. C# is the primary programming language for .NET and much of .NET is written in C#.

Expand All @@ -54,31 +55,31 @@ Exceptions are the primary error handling model in .NET. Exceptions have the ben

App stacks, like ASP.NET Core and Windows Forms, build on and take advantage of low-level libraries, language, and runtime. The app stacks define the way that apps are constructed and their lifecycle of execution.

The SDK and other tools enable a modern developer experience, both on a developer desktop and for continuous integration (CI). The modern developer experience includes being able to build, analyze, and test code. .NET projects can often be built by a single `dotnet build` command, which orchestrates restoring NuGet packages and building dependencies.
The SDK and other tools enable a modern developer experience, both on a developer desktop and for continuous integration (CI). The modern developer experience includes building, analyzing, and testing code. .NET projects can often be built by a single `dotnet build` command, which orchestrates restoring NuGet packages and building dependencies.

NuGet is the package manager for .NET. It contains hundreds of thousands of packages that implement functionality for many scenarios. A majority of apps rely on NuGet packages for some functionality. The [NuGet Gallery](https://nuget.org/) is maintained by Microsoft.

## Free and open source

.NET is free, open source, and is a [.NET Foundation](https://dotnetfoundation.org/) project. .NET is maintained by Microsoft and the community on GitHub in [several repositories](https://github.com/dotnet/core/blob/main/Documentation/core-repos.md).

.NET source and binaries are licensed with the [MIT license](https://github.com/dotnet/runtime/blob/main/LICENSE.TXT). Additional [licenses apply on Windows](https://github.com/dotnet/core/blob/main/license-information-windows.md).
.NET source and binaries are licensed with the [MIT license](https://github.com/dotnet/runtime/blob/main/LICENSE.TXT). Other [licenses apply on Windows](https://github.com/dotnet/core/blob/main/license-information-windows.md).

## Support

.NET is [supported by multiple organizations](https://github.com/dotnet/core/blob/main/support.md) that work to ensure that .NET can run on [multiple operating systems](https://github.com/dotnet/core/blob/main/os-lifecycle-policy.md) and is kept up to date. It can be used on Arm64, x64, and x86 architectures.

New versions of .NET are released annually in November, per our [releases and support policies](releases-and-support.md). It is [updated monthly](https://github.com/dotnet/announcements/labels/Monthly-Update) on Patch Tuesday (second Tuesday), typically at 10 AM Pacific time.
New versions of .NET are released annually in November, per the [releases and support policies](releases-and-support.md). It's [updated monthly](https://github.com/dotnet/announcements/labels/Monthly-Update) on Patch Tuesday (second Tuesday), typically at 10 AM Pacific time.

## .NET ecosystem

There are multiple variants of .NET, each supporting a different type of app. The reason for multiple variants is part historical, part technical.
Multiple variants of .NET exist, each supporting a different type of app for both historical and technical reasons.

.NET implementations:

* **.NET (Core)** -- Modern .NET. A cross-platform and open source implementation of .NET, rethought for the cloud age while remaining significantly compatible. It is evolving and actively supported.
* **.NET Framework** -- The original .NET. It provides access to the broad capabilities of Windows and Windows Server. It is actively supported, in maintenance.
* **Mono** -- The original community and open source .NET. A cross-platform implementation of .NET Framework.
* **.NET (Core)** — Modern .NET. A cross-platform and open-source implementation of .NET, rethought for the cloud age while remaining significantly compatible. It's evolving and actively supported.
* **.NET Framework** — The original .NET. It provides access to the broad capabilities of Windows and Windows Server. It's actively supported, in maintenance.
* **Mono** — The original community and open-source .NET. A cross-platform implementation of .NET Framework.

## Next steps

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