AspNetCore.Docs/aspnetcore/index.md

---
title: Introduction to ASP.NET Core
author: rick-anderson
description: Get an introduction to ASP.NET Core, a cross-platform, high-performance, open-source framework for building modern, cloud-based, Internet-connected applications.
manager: wpickett
ms.author: riande
ms.date: 02/28/2018
ms.prod: asp.net-core
ms.technology: aspnet
ms.topic: article
uid: index
---
# Introduction to ASP.NET Core

By [Daniel Roth](https://github.com/danroth27), [Rick Anderson](https://twitter.com/RickAndMSFT), and [Shaun Luttin](https://twitter.com/dicshaunary)

ASP.NET Core is a cross-platform, high-performance, [open-source](https://github.com/aspnet/home) framework for building modern, cloud-based, Internet-connected applications. With ASP.NET Core, you can:

* Build web apps and services, [IoT](https://www.microsoft.com/internet-of-things/) apps, and mobile backends.
* Use your favorite development tools on Windows, macOS, and Linux.
* Deploy to the cloud or on-premises.
* Run on [.NET Core or .NET Framework](https://docs.microsoft.com/dotnet/articles/standard/choosing-core-framework-server).

## Why use ASP.NET Core?

Millions of developers have used (and continue to use) [ASP.NET 4.x](https://docs.microsoft.com/aspnet/overview) to create web apps. ASP.NET Core is a redesign of ASP.NET 4.x, with architectural changes that result in a leaner, more modular framework.

ASP.NET Core provides the following benefits:

* A unified story for building web UI and web APIs.
* Integration of [modern, client-side frameworks](xref:client-side/index) and development workflows.
* A cloud-ready, environment-based [configuration system](xref:fundamentals/configuration/index).
* Built-in [dependency injection](xref:fundamentals/dependency-injection).
* A lightweight, [high-performance](https://github.com/aspnet/benchmarks), and modular HTTP request pipeline.
* Ability to host on [IIS](xref:host-and-deploy/iis/index), [Nginx](xref:host-and-deploy/linux-nginx), [Apache](xref:host-and-deploy/linux-apache), [Docker](xref:host-and-deploy/docker/index), or self-host in your own process.
* Side-by-side app versioning when targeting [.NET Core](https://docs.microsoft.com/dotnet/articles/standard/choosing-core-framework-server).
* Tooling that simplifies modern web development.
* Ability to build and run on Windows, macOS, and Linux.
* Open-source and [community-focused](https://live.asp.net/).

ASP.NET Core ships entirely as [NuGet](https://www.nuget.org/) packages. Using NuGet packages allows you to optimize your app to include only the necessary dependencies. In fact, ASP.NET Core 2.x apps targeting .NET Core only require a [single NuGet package](xref:fundamentals/metapackage). The benefits of a smaller app surface area include tighter security, reduced servicing, and improved performance.

## Build web APIs and web UI using ASP.NET Core MVC

ASP.NET Core MVC provides features to build [web APIs](xref:tutorials/index#build-web-apis) and [web apps](xref:tutorials/index#build-web-apps):

* The [Model-View-Controller (MVC) pattern](xref:mvc/overview) helps make your web APIs and web apps [testable](xref:test/index).
* [Razor Pages](xref:mvc/razor-pages/index) (new in ASP.NET Core 2.0) is a page-based programming model that makes building web UI easier and more productive.
* [Razor markup](xref:mvc/views/razor) provides a productive syntax for [Razor Pages](xref:mvc/razor-pages/index) and [MVC views](xref:mvc/views/overview).
* [Tag Helpers](xref:mvc/views/tag-helpers/intro) enable server-side code to participate in creating and rendering HTML elements in Razor files.
* Built-in support for [multiple data formats and content negotiation](xref:web-api/advanced/formatting) lets your web APIs reach a broad range of clients, including browsers and mobile devices.
* [Model binding](xref:mvc/models/model-binding) automatically maps data from HTTP requests to action method parameters.
* [Model validation](xref:mvc/models/validation) automatically performs client- and server-side validation.

## Client-side development

ASP.NET Core integrates seamlessly with popular client-side frameworks and libraries, including [Angular](xref:spa/angular), [React](xref:spa/react), and [Bootstrap](xref:client-side/bootstrap). For more information, see [Client-side development](xref:client-side/index).

## ASP.NET Core targeting .NET Framework

ASP.NET Core can target .NET Core or .NET Framework. ASP.NET Core apps targeting .NET Framework aren't cross-platform—they run on Windows only. There are no plans to remove support for targeting .NET Framework in ASP.NET Core. Generally, ASP.NET Core is made up of [.NET Standard](/dotnet/standard/net-standard) libraries. Apps written with .NET Standard 2.0 run anywhere that .NET Standard 2.0 is supported.

There are several advantages to targeting .NET Core, and these advantages increase with each release. Some advantages of .NET Core over .NET Framework include:

* Cross-platform. Runs on macOS, Linux, and Windows.
* Improved performance
* Side-by-side versioning
* New APIs
* Open source

We're working hard to close the API gap from .NET Framework to .NET Core. The [Windows Compatibility Pack](/dotnet/core/porting/windows-compat-pack) made thousands of Windows-only APIs available in .NET Core. These APIs weren't available in .NET Core 1.x.

## Next steps

For more information, see the following resources:

* [Get started with Razor Pages](xref:tutorials/razor-pages/razor-pages-start)
* [ASP.NET Core tutorials](xref:tutorials/index)
* [ASP.NET Core fundamentals](xref:fundamentals/index)
* [The weekly ASP.NET community standup](https://live.asp.net/) covers the team's progress and plans. It features new blogs and third-party software.