When multiple modules exist, netlistsvg just uses the first one.

[mithro]

If you have multiple modules in your JSON file, netlistsvg uses the first one found in the file. As yosys outputs an alphabetically ordered file, this isn't probably what people want.

Instead they probably want the module which is marked as the 'top'; see below;

    "MUX4": {
      "attributes": {
        "top": 1,
        "src": "sim.v:3"
      },
      "ports": {
        "I0": {
          "direction": "input",
          "bits": [ 2 ]
        },
        "I1": {

[mithro]

This should be fixed in #2