The High-Level Shader Language or High-Level Shading Language (HLSL) is a proprietary shading language developed by Microsoft for the Direct3D 9 API to augment the shader assembly language, and went on to become the required shading language for the unified shader model of Direct3D 10 and higher.

HLSL is the C-like high-level shader language that you use with programmable shaders in DirectX. For example, you can use HLSL to write a vertex shader, or a pixel shader, and use those shaders in the implementation of the renderer in your Direct3D application.

The hlsl is the GPU programming language provided in conjunction with the dx runtime. Over many years its use has expanded to cover every major rendering API across all major development platforms. Despite its popularity and long history hlsl has never had a formal language specification.