ASP.NET Core

ASP.NET Core is the open-source framework Microsoft maintains for building web apps, HTTP APIs, and cloud-connected backends on .NET. It's aimed at developers who want a modular, high-performance runtime that works the same way on Windows, macOS, and Linux, whether you're shipping a REST API, a server-rendered site with Razor, or a backend for a mobile app.

The project is the actual source for the ASP.NET Core shared framework that ships with the .NET SDK. Most developers won't build it from source; they'll install the .NET SDK and use ASP.NET Core through project templates and NuGet packages. This repo matters most if you want to track development, file issues, contribute code, or grab nightly builds ahead of an official release.

Key features

• Cross-platform runtime: apps built with ASP.NET Core run unmodified on Windows, macOS, and Linux, including musl-based distros.
• Modular components: the framework is split into composable pieces with minimal overhead, so you only pull in what your app needs.
• Razor support: server-rendered views and Razor Pages/components use the Razor syntax (.cshtml, .razor), backed by a dedicated compiler and tooling.
• Web and API hosting: build MVC-style web apps, minimal APIs, or backends for mobile and IoT apps on the same stack.
• IIS and Kestrel hosting options: deploy behind IIS on Windows using the ASP.NET Core Module, or run the built-in Kestrel server directly on any platform.
• Nightly builds: daily builds of the shared framework and Windows Hosting Bundle are published for Windows, macOS, and Linux across x64, x86, and arm64.
• Active governance: part of the .NET Foundation, with a public roadmap, weekly community standup, and documented triage process for issues.

Ideal use cases

ASP.NET Core is a solid fit if you're building server-side web applications, JSON/REST APIs, or backends that need to run in containers or on-premises, and you want a single framework that spans web, mobile backend, and IoT scenarios. It also fits teams already invested in .NET who want to share code (models, validation, business logic) between a web frontend and other .NET services.

It's a good match for contributors who want to work on the framework itself: fixing bugs, adding features, or testing nightly builds against real workloads before general release. The repo's "good first issue" and "help wanted" labels make it approachable for first-time open-source contributors.

It's not the right choice if you just want to consume ASP.NET Core in an app; you don't need this repo for that, just the .NET SDK. It's also not a fit if your stack has no room for .NET, or if you need a framework for a language other than C#/.NET (F# and VB are supported by the runtime, but the framework itself targets .NET generally).

Installation

Most developers should skip building this repo and instead install the .NET SDK, which bundles the ASP.NET Core shared framework along with everything except the IIS plugin. Get it from the .NET homepage and follow the official Getting Started guide.

If you specifically need the latest daily build of the ASP.NET Core Shared Framework or the Windows Hosting Bundle, download it from the nightly builds table in the repo, choosing the installer or binary archive for your platform (Windows x64/x86/arm64, macOS x64/arm64, or Linux x64/arm/arm64, including musl variants).

To work on the framework source itself:

git clone https://github.com/dotnet/aspnetcore.git
cd aspnetcore

Then follow the detailed steps in docs/BuildFromSource.md for the prerequisites and build commands specific to your OS. Before opening a pull request, read CONTRIBUTING.md for coding guidelines and the issue triage process.