> So just to be sure: the list of URLs + metadata that gets used for stable diffusion is several terabytes. Not the images. Just the list of URLs alone (and a bit of other metadata). > Stable diffusion itself is just 6+ GB, and fits comfortably on my USB stick.

Thanks for sharing this info which I'm aware of. However, this fact is not as significant as it might sound in terms of whether it's a lossy compression algorithm.

In most lossy compression algorithms, the compression rate is arbitrary. For example, for an algorithm that based on fourier transform, you can choose only take the first sin wave, or the first 1000 ones (a bit oversimplification here).

So yes, SD is small. Quite miracally small, and its size alone implies some important insights on how human see and read artworks. But this fact doesn't change whether I see it as a lossy compression. (In my previous comment I stated human brain stores lossy compressed data too, so you can see I'm using a broad definition of "lossy compression".)