VRM viewer

Drop the .vrm file on the box above. The avatar loads facing you with its skeleton drawn on top: drag to turn it 360°, scroll to zoom, right-drag to pan. The panel next to it lists the avatar's name, author, VRM version, how many humanoid bones it maps, and what its license says about commercial use.

VRM files rarely carry animation clips, so use Bend test to see how the avatar deforms: it swings every bone in turn, then sways the whole body, and bad weights show up as tearing or collapsing geometry.

The Skeleton toggle draws every bone as a line from parent to child, with a dot on each joint, so fingers, jaws and other end bones stay visible too. The side panel lists the whole hierarchy with each bone's name and how many vertices it moves. Bones that move nothing are greyed out: usually end bones, IK targets or helpers you can delete before export.

Click anywhere on the model and the viewer selects the bone that moves that spot the most, which is the quickest way to find out which of "bone_23" and "bone_24" is the left forearm.

Turn on Skin weights and each bone gets its own color, blended where vertices share bones, so you see where one bone's area ends and the next begins. Select a bone and the view switches to a heat map with the same blue-to-red ramp as Blender's weight paint: red moves fully with the bone, green about half, blue not at all.

The problems that show up most: a thigh bone that also pulls the other leg, a hand whose weights stop dead at the wrist, a shoulder with a hard edge where it should fade, and stray vertices on the chest weighted to an arm. Bend test swings each bone 45° in turn and then sways the whole rig, so bad weights show up as tearing or collapsing even on a model without animation.

VRM is the avatar format behind VRoid Studio, VSeeFace and most VTuber apps. Under the hood it's a GLB with extra rules: a humanoid bone map, facial expressions, spring bones for hair and clothes, and a license block that says who may use the avatar and how. The viewer reads both VRM 0.x and VRM 1.0.

MToon toon shading and spring-bone physics aren't simulated, so the avatar shows its base colors and the hair stays still. The mesh, the skeleton and the skin weights are exactly what's in the file.