We introduce a sparse volumetric data structure, dubbed NanoVDB, which is portable to both C++11 and C99 as well as most graphics APIs, e.g. CUDA, OpenCL, OpenGL, WebGL, DirectX 12, OptiX, HLSL, and GLSL. As indicated by its name, NanoVDB is a mini-version of the much bigger OpenVDB library, both in terms of functionality and scope. However, NanoVDB offers one major advantage over OpenVDB, namely support for GPUs. As such it is applicable to both CPU and GPU accelerated simulation and rendering of high-resolution sparse volumes. In fact, it has already been adopted for real-time applications by several commercial renders and digital content creation tools, e.g. Autodesk’s Arnold, Blender, SideFX’s Houdini, and NVIDIA’s Omniverse just to mention a few.