Convert GRO to glTF (Free)
Also converts STL, OBJ, GLB, PLY, USDZ, 3MF from the same file.
Runs in your browser. No upload, no signup, nothing to install.
Also from Innerscene: Circadian Lab, a free lighting calculator for room illuminance, melanopic EML, and glare.
How to convert GRO to glTF
- 1
Open your .gro file
Drag it onto the viewer above, or click "Open a GRO File". Files up to 200 MB open directly; the parse runs in a worker so the page stays responsive.
- 2
Click Download glTF
Once the file is open, the Download glTF button sits at the bottom right of the viewer. The Export menu in the toolbar has every other format.
- 3
Download
The .gltf is written in the browser and saved straight to your downloads folder. No queue, no email, no watermark.
What survives the conversion
A file conversion is a translation, and formats do not carry the same things. Here is exactly what moves from GRO into glTF, and what does not.
| Geometry | Kept | Both formats store triangle meshes, so the shape transfers directly. |
|---|---|---|
| Colors and materials | Kept | glTF carries full PBR materials, which is at least what GRO stores, so the colors come across. |
| Layers and structure | Kept | Layers survive as real layers in the glTF file, so you can still isolate and toggle them. |
| Units and scale | Reduced | GRO coordinates are in ångströms, and the export treats one ångström as one meter: a protein 50 Å across arrives 50 meters across. Scale the model on import to the size you want. |
What the glTF writer emits: The GLB export unpacked into its two parts: a JSON `.gltf` with `buffers[0]` pointing at an external `${base}.bin` (the source file’s own base name), zipped together.
The source: GROMACS structure (GRO) (.gro)
A GROMACS structure converted from nanometres to ångströms: proteins as a cartoon of their chains, other molecules as ball and stick, water, hydrogens and space filling on layers of their own, and a rectangular simulation box drawn as the unit cell. Bonds are worked out from covalent radii.
The target: glTF separate (.gltf + .bin) (.gltf)
The same glTF scene as the GLB export, as the loose JSON and binary files some pipelines expect instead of one packed file.
Opens in: Blender, Unity, Unreal Engine, model-viewer, any glTF-separate pipeline.
Your file never leaves your computer
Both the GRO parser and the glTF writer are JavaScript and WebAssembly running in your own browser tab. There is no upload step, no server-side conversion queue, and no copy of your file anywhere but your machine. That matters for drawings under NDA, for client work, and for anything you would not email to a stranger.
Free to Use, No Signup
There are no accounts and no watermarks on this converter. If it saved you time, the one thing we ask is a mention: a post, a link from your blog or course page, or a reply to someone asking how to open a file.
Share it
Made something reusable? Add it to the Free Parts Library. Writing about it? Copy a link, badge or citation. Send us your post and we’ll feature it with a link to your site.
Hear about new formats
Occasional emails when the viewer learns a new format or gets a new tool.
Frequently asked questions
▶Is this GRO to glTF converter free?
Yes. No signup, no watermark, no per-file limit and no paid tier. Innerscene.
▶Is my GRO file uploaded anywhere?
No. The file is read with the browser file API and converted in the same tab. Nothing is sent to a server unless you explicitly click Share, which is a separate, opt-in feature.
▶Will my colors and materials survive the glTF export?
glTF carries full PBR materials, which is at least what GRO stores, so the colors come across.
▶Do layers and named parts carry into the glTF file?
Layers survive as real layers in the glTF file, so you can still isolate and toggle them.
▶Will the glTF open at the right size?
GRO coordinates are in ångströms, and the export treats one ångström as one meter: a protein 50 Å across arrives 50 meters across. Scale the model on import to the size you want.
▶How large a GRO file can I convert?
Up to 200 MB, and the ceiling adapts to how much memory your device reports. The conversion runs on your own hardware, so a desktop with plenty of RAM will handle more than a phone.
▶Can I convert glTF back to GRO?
Not here. We read GRO and write glTF, but not the reverse. the universal 3D viewer
▶Which browsers does it work in?
Chrome, Edge, Firefox and Safari, on Windows, macOS, Linux, iOS and Android. No plugin and no extension.
Convert GRO to something else
Convert something else to glTF
Or start from the universal 3D viewer.