How to edit a GLB file

What is actually inside a GLB

A GLB is a 12-byte header followed by two chunks: a JSON description of the scene, and one binary blob holding the vertex and index data. The JSON names every node, mesh, material and accessor; the binary is raw numbers the JSON points into.

• Nodes carry the names and the transforms — this is where part names live.
• Meshes hold primitives, each with attributes (position, normal, UV) and one material.
• Materials are PBR values: base colour, metallic, roughness, plus optional texture references.
• Repeated parts are multiple nodes pointing at one mesh, which is why a well-built GLB with sixty columns can be tiny.

Opening a GLB

Editing one part of a GLB

1. 01Import and read the outlinerImport the GLB into Blender. A well-built file appears as named objects under one empty. If everything is one object, separate it first — select connected geometry with L, split with P, and name the pieces.
2. 02Select the part by nameWork from the outliner rather than clicking in the viewport, so you know exactly which node you have.
3. 03Note the numbers you must keepDimensions of the part and of anything it mates with. GLB is metres by default, so a 460 mm seat is 0.46 units.
4. 04Edit in Edit ModeChanging the mesh rather than the object transform keeps the node's translation intact — important, because other parts are positioned relative to it.
5. 05Keep the material assignmentIf you add geometry to a part, assign it the part's existing material rather than a new one, or the export gains a material nobody asked for.
6. 06Export as glTF BinaryFile → Export → glTF 2.0, format glTF Binary (.glb). Leave “Custom Properties” and “Y up” at their defaults unless the target engine needs otherwise.

Keeping part names through a round trip

The most common loss in a GLB edit is not geometry — it is naming. Names are what make a part addressable in code and in any later edit, and several habits destroy them silently.

• Joining objects (Ctrl+J) merges parts into one node and discards the names of everything but the active object.
• Applying a modifier that merges by distance across parts can weld separate pieces into one.
• Exporting only the selection while the parent empty is unselected can flatten the hierarchy.
• Auto-generated names — Cube.003 — are a smell: something was recreated rather than edited.

After exporting, re-import your own file and read the outliner. Thirty seconds of checking catches a round trip that quietly cost you the structure.

Editing a GLB with Refora

Refora imports a model, analyses it into parts with dimensions and triangle counts, and lets you scope a plain-language request to one part or a repeated group. GLB is its audited round trip: geometry, part names, materials and embedded preset images survive export and re-import. Other formats are listed as each one is verified in a release build.