A formal specification of the APIs that are common across .NET implementations
What is .NET Standard?
There are various implementations of .NET. Each implementation allows .NET code to execute in different places—Linux, macOS, Windows, iOS, Android, and many more. .NET Standard is a formal specification of the APIs that are common across all these .NET implementations.
.NET Standard allows libraries to build against the agreed on set of common APIs, ensuring they can be used in any .NET application—mobile, desktop, IoT, web, or anywhere you write .NET code.
.NET Standard versions
.NET Standard is versioned. Each new version adds more APIs. When a library is built against a certain version of .NET Standard, it can run on any .NET implementation that implements that version of .NET Standard (or higher).
Targeting a higher version of .NET Standard allows a library to use more APIs, but means it can only be used on more recent versions of .NET. Targeting a lower version reduces the available APIs, but means the library can run in more places.