Tiny Online Tools
A STEP or IGES file rarely stores a single lump of geometry — it stores a product structure: an assembly made of sub-assemblies, made of parts, each one a boundary-representation (B-Rep) solid described by exact surfaces rather than triangles. That structure is the whole point of the format, but most viewers throw it away the moment they tessellate the file, leaving you with one flat pile of meshes and no way to tell a bracket from a bolt.
This tool keeps the structure. It reads the file with the same OpenCascade kernel used across the site's other CAD tools, walks the product tree it returns, and shows it to you as a collapsible hierarchy — which nodes are assemblies, which are leaf parts, and how many meshes, vertices and triangles live under each one. Click any node, part or whole sub-assembly, and it renders in isolation in the 3D preview so you can confirm you have the right one before doing anything with it.
A few honest notes: the vertex and triangle counts are a property of this tessellation pass, not of the underlying geometry — raise the quality preset and they climb, because OpenCascade is re-approximating the same exact surfaces more finely. The one number that does not move with quality is the B-Rep face count shown for a single-solid part, since that comes straight from the kernel's surface list rather than the triangle mesh. Everything runs locally in your browser; the file never leaves your machine.
Useful before importing a large assembly into a mesh-only workflow, auditing a supplier's STEP export for how it's actually organized, or just answering "how many parts are actually in this thing?" without opening a full CAD package.