Find unsupported APIs in your code

APIs in your .NET Framework code may not be supported in .NET for many reasons. These reasons range from the simple to fix, such as a namespace change, to the more challenging to fix, such as an entire technology not being supported. The first step is to determine which of your APIs are no longer supported and then identify the proper fix.

Important

.NET Upgrade Assistant is officially deprecated. Use the GitHub Copilot modernization chat agent instead, which is included with Visual Studio 2026 and Visual Studio 2022 17.14.16 or later. This agent analyzes your projects and dependencies, produces a step-by-step migration plan with targeted recommendations and automated code fixes, and commits each change so you can validate or roll back. It automates common porting tasks—updating project files, replacing deprecated APIs, and resolving build issues—so you can modernize faster with less manual effort.

.NET Portability Analyzer

Important

API Port has been deprecated in favor of binary analysis with the .NET Upgrade Assistant tool. The backend service of API Port has been shut down, so to use the tool, you must use it offline. For more information, see .NET API Port README.

The .NET Portability Analyzer is a tool that analyzes assemblies and provides a detailed report on .NET APIs that are missing for the applications or libraries to be portable on your specified targeted .NET platforms.

To use the .NET Portability Analyzer in Visual Studio, install the extension from the marketplace.

For more information, see The .NET Portability Analyzer.