In .NET, one of the important features for performance and memory management is ReadOnlySpan<T>. In this article, we will explore what ReadOnlySpan<T> is, how to use it, and its technical details. Additionally, we will look at how it translates to IL code and compare it to other collection types. What is ReadOnlySpan<T>? ReadOnlySpan<T> is a type introduced in .NET Core 2.1 that provides a type-safe and memory-safe representation of a contiguous region of arbitrary memory.