How does Sketchfab determine if a 3D model uses PBR materials?

When browsing 3D models on Sketchfab, especially within Downloadable and Store searches, you may notice that we mark models as using PBR materials or not.

You will see PBR listed as "Metalness", "Specular", or "No", depending on the workflow the model uses.

For a model to be listed as PBR, it must meet the following requirements:

• Use the PBR renderer (not Matcap)
• Use Lit shading (not Shadeless)
• Include a texture in the Metalness or Specular channel of each material (depending on the workflow)
• Include a texture in the Roughness/Glossiness channel of each material