The format the web ships 3D in. Reducing the triangle count is what makes a model load quickly on a phone.
—
80
Resize
50
Encoder detail
6
fastzopfli
256
28
0 lossless51 tiny
The largest saving available.
50
Speed, audio and advanced
8
0 smallest13 fastest
128
96
Advanced
8
Nearly all of the saving comes from the images inside.
150
75
Advanced
50
aggressivegentle
Advanced
14
coarsefine
0 merges only exactly equal vertices. A small value also closes hairline cracks left by CAD exporters.
Geometry only — texture coordinates,
materials and vertex colours are not carried through. Decimating a
UV-mapped mesh correctly is a much harder problem, and mangling your
UVs quietly would be worse than leaving them alone.
12
6
Advanced
ZIP and 7z. 7z encrypts the file list too.
What actually shrinks glTF / GLB files
Node transforms are baked into the vertices on read, so an assembled model stays assembled.
Output is always GLB rather than JSON glTF: a .gltf has to base64 its buffer, which inflates it by a third for no benefit.
A .gltf that points at a separate .bin cannot be resolved from a single upload — export a .glb instead, and the tool says so rather than failing obscurely.
Materials, textures, animations and skins are not carried through. This works on geometry.