Open 0xr.space, press Open and choose the .step, .stp, .iges, .igs, .brep or .FCStd. It is meshed in the browser by OpenCascade, the kernel FreeCAD uses, compiled to WebAssembly, with face and body colours and part names kept and the file's units converted to metres. You can turn it, cut through it, pull its parts apart and place it at real size on a desk on a Quest or an ARCore phone.
It is a viewer, not CAD: the assembly tree is flattened into named parts, the mesh resolution is fixed, and there is no measuring between edges, no PMI and no export back to STEP. Assemblies over 4 million triangles are refused. A FreeCAD file shows its visible solids; linked objects are not followed yet.
Yes for STEP and IGES, which say their unit. A FreeCAD file is millimetres. A bare BREP has no unit and is shown in its own numbers.
Part names are kept, but the tree is flattened: every part is placed where the assembly puts it, without the sub-assembly grouping.
Info gives the overall size, volume and whether a part is watertight, and Measure takes an approximate distance between two points. There is no edge-to-edge measuring and no export back to STEP; with a free account the model can be downloaded as GLB, STL or USDZ from its card's three-dot menu on Home.
No. It is read on the device, and nothing is sent to a server unless you create a share link yourself.