What Is GLSL? GLSL (GLslang) is a short term for the official OpenGL Shading Language. GLSL is a C/C++ similar high level programming language for several parts of the graphic card. With GLSL you can code (right up to) short programs, called shaders, which are executed on the GPU. Why Shaders? Until DirectX 8 hardware (GeForce 2 and lower, Radoen 7000 and lower) the graphic pipeline could only be