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The Khronos Group publishes interoperability specifications for graphics and related computational interfaces. Its OpenGL specification defines a rendering pipeline, including rasterization, fragment shaders and per-fragment operations. A specification makes observable behavior portable across implementations: for example, a configured depth buffer comparison determines whether a candidate surface contributes to the framebuffer. This is a definition of an interface contract, rather than a requirement that all implementations use identical internal hardware.^[ref][ref]

OpenGL is a graphics programming interface that specifies commands, data objects and rendering behavior independently of a particular graphics processor. An application supplies geometric primitives and programs for programmable stages; the implementation transforms, rasterizes and combines their contributions into a framebuffer. Khronos Group publishes the specification, including the distinction between core and compatibility profiles.^[ref]

For example, drawing an opaque triangle requires vertex data, appropriate shader programs and a draw command. The triangle can generate fragments during rasterization; a fragment shader determines their candidate outputs, and a depth buffer test can reject hidden contributions. The interface specifies the results these operations must produce, while implementations can use different internal hardware and scheduling. A rendering command's submission is also distinct from completion of the corresponding device work.^[ref]