texture-compression-bc

BC formats store textures compressed in GPU memory (typically 4:1 to 8:1), which cuts VRAM use and, more importantly, memory bandwidth during sampling. BC7 offers high-quality RGBA, BC5 two-channel data for normal maps, BC6H HDR - a complete toolkit for shipped game content.

BC is a desktop-GPU family: essentially universal on Windows, Linux, and Intel/AMD/NVIDIA hardware, and supported on Apple silicon Macs. Mobile GPUs instead implement ETC2/ASTC, which is why WebGPU guarantees that at least one of the compressed-texture families is available but not which one.

Portable applications ship the same content in two or three compressed encodings and pick at runtime - the availability numbers for BC, ETC2, and ASTC on this site tell you exactly what the split looks like in the field.