It's useful to bucket these in magnitudes for the ability to run both layout and rendering. D3 is great up to ~5000 elements, sigma is probably the best open so

It's useful to bucket these in magnitudes for the ability to run both layout and rendering. D3 is great up to ~5000 elements, sigma is probably the best open source and reaches up to ~50K (?). And, shameless plug, we've focused on bigger ones, and regularly do 1MM :) (See PyGraphistry link above.) For smaller graphs, the focus is generally more on styling, like SVG, so D3 is probably better. Larger graphs are used in analytic workloads like machine learning, network operations, etc. The emphasis is more on the ability to see big graphs (requiring smart rendering and layout), bind algorithm results to the visual encoding, and drill down. D3 and pure rendering libraries become a bit too low-level and clunky at this point.