GLB vs FBX vs USDZ vs OBJ vs BLEND: File Sizes Measured

“Which format is smallest?” sounds like a simple question, but the answer depends heavily on the model. So instead of guessing, we read the file sizes of every finished download package in the Grab3D library and put them side by side. Short version: none of our downloads use mesh compression, so the formats sit closer together than many people expect. For detailed models the FBX is a median 1.72× the size of the GLB, and the zipped OBJ even comes out smaller than the GLB. The real size saver is the light GLB: a median 44 % of the full GLB.

How we measured

• Data: 739 finished download packages as of 30 September 2026 (715 models plus 24 rigged variants). This includes models scheduled for later release waves, not only the ones already online.
• Tiers: 102 High Detail models (median around 800,000 triangles, 4K PBR textures), 613 Lightweight models (median 14,086 triangles, mostly 2K textures, while the 30 low poly models use a tiny palette texture) and the 24 rigged packages.
• Compression: none. Since 30 September 2026 every GLB download (full, light and rigged) is stored without Draco or Meshopt compression. Only the 3D preview on the website is Draco-compressed.
• Source: the byte sizes are read from each package’s manifest file, which is written when the files are exported. Nothing is estimated.
• Statistics: median plus the interquartile range (p25–p75, the middle half of all packages), because a few very large models would distort an average. “Ratio” is the median of the per-model ratio to that model’s GLB.
• Units: 1 MB = 1,048,576 bytes (MiB), GB likewise binary.
• Formats: GLB, FBX, .blend, USDZ and OBJ (zipped with MTL and textures). Rigged variants ship GLB, FBX and .blend only.

All packages at a glance

Format	Packages	Median	Middle half (p25–p75)	Smallest to largest	Total
GLB	739	1.27 MB	0.86–2.06 MB	0.07–38.84 MB	3.40 GB
FBX	739	2.23 MB	1.50–3.44 MB	0.06–66.37 MB	5.56 GB
BLEND	739	1.13 MB	0.76–1.76 MB	0.12–41.88 MB	3.87 GB
USDZ	715	1.96 MB	1.34–2.96 MB	0.08–51.46 MB	4.78 GB
OBJ-ZIP	715	1.14 MB	0.75–1.80 MB	0.02–29.48 MB	2.47 GB

Because most of the library is Lightweight, the overall medians look close. The totals show the full picture: all FBX files together are 1.63× the size of all GLBs, and most of that difference comes from the High Detail models.

High Detail models (n = 102)

Format	Median	Middle half (p25–p75)	Ratio to GLB
GLB	26.13 MB	19.37–28.12 MB	1×
FBX	46.41 MB	32.65–48.43 MB	1.72×
USDZ	41.61 MB	29.85–43.44 MB	1.56×
BLEND	32.90 MB	23.81–34.76 MB	1.24×
OBJ-ZIP	19.41 MB	14.46–21.37 MB	0.76×
light GLB	11.71 MB	8.05–12.20 MB	0.44×
light FBX	23.18 MB	15.83–24.04 MB	0.49× of the full FBX

Example: the samurai comes as a 29.4 MB GLB, 51.4 MB FBX, 36.4 MB .blend, 46.2 MB USDZ and 24.3 MB OBJ-ZIP, plus a 12.2 MB light GLB and a 24.2 MB light FBX.

Lightweight models (n = 613)

Format	Median	Middle half (p25–p75)	Ratio to GLB
GLB	1.12 MB	0.78–1.55 MB	1×
FBX	1.97 MB	1.37–2.68 MB	1.75×
USDZ	1.78 MB	1.26–2.41 MB	1.59×
BLEND	1.01 MB	0.70–1.33 MB	0.89×
OBJ-ZIP	1.01 MB	0.69–1.41 MB	0.90×
light GLB (122 models)	0.89 MB	0.78–1.07 MB	0.52×
light FBX (122 models)	1.65 MB	1.39–1.84 MB	0.55× of the full FBX

The geometry is small here, so the .blend and the zipped OBJ even come out slightly smaller than the GLB. Only 122 of the 613 Lightweight models have a light variant. It is only built for models with at least 20,000 triangles, and only when it removes at least 30 % of them.

Rigged characters (n = 24)

Format	Median	Middle half (p25–p75)	Ratio to GLB
GLB	12.82 MB	12.39–13.38 MB	1×
FBX	11.07 MB	10.56–11.93 MB	0.87×
BLEND	13.05 MB	12.34–14.02 MB	1.01×

Rigged variants have 216,000–300,000 triangles, 2K textures and two animation clips (walk and run). All three formats end up at roughly the same size. There is no USDZ or OBJ for them, and OBJ can’t store a skeleton anyway. How to use them is covered in the rigged character guide.

The chart: every format relative to the GLB

Draco: what it saved, and why our downloads skip it

Until 29 September 2026 the full-quality GLBs of High Detail models and all rigged GLBs were Draco-compressed. We measured both versions of the same files: Draco made the High Detail GLBs a median 3.62× smaller (6.51 MB instead of 26.13 MB) and the rigged GLBs 4.74× smaller (2.70 MB instead of 12.82 MB).

That saving had a price. Godot’s glTF importer cannot read Draco at all, Unity’s glTFast needs the extra Draco for Unity package, and not every other tool decodes it either. So since 30 September 2026 every download is uncompressed for maximum compatibility: the GLB opens directly in Godot 4, in Unity with glTFast alone, in Unreal Engine 5 and in Blender. Only the 3D preview on the website still uses Draco, because in the browser fast loading matters and the viewer decodes it anyway.

Tip: if you want the smaller file anyway, for example for a web game, compress a copy yourself with gltf-transform: npx @gltf-transform/cli draco model.glb model-draco.glb or npx @gltf-transform/cli meshopt model.glb model-meshopt.glb. Keep the original for engines that can’t decode the result.

The light GLB is the real size saver

For High Detail models the light GLB is a median 44 % of the full GLB (21–51 % across all 102 models). It has roughly half the triangles and 1K instead of 4K textures, so it is lighter at runtime (fewer triangles to draw, much less texture memory) and a much smaller download. For Lightweight models that have one, the light GLB is 0.52× the full GLB.

Why FBX, USDZ and BLEND are bigger for High Detail

• Embedded textures. Each package carries four 4K PBR maps (base color, roughness, metallic, normal). The FBX embeds them, the .blend has them packed, and the USDZ bundles them. A USDZ is a zip archive whose contents are stored without compression, by design of the format.
• Format overhead. The GLB stores vertices and indices as compact binary buffers. FBX, USDZ and .blend carry the same mesh of around 800,000 triangles with more overhead, which adds up at this density.
• OBJ is zipped. OBJ itself is plain text and large, but we ship it as a ZIP. Compression recovers so much that OBJ-ZIP is the smallest High Detail download (0.76× the GLB, smaller than the GLB for 101 of 102 models). The catch: OBJ has no PBR material standard and no real-world scale.

For Lightweight models the geometry is small (median 14,086 triangles) and the textures are 2K or tiny palettes, so the formats end up within a factor of about two of each other.

Which file for which engine?

Unity

The FBX imports without any package, but for High Detail models it is the largest download (median 46.41 MB). The GLB is smaller (median 26.13 MB) and needs only a glTF package (glTFast or UnityGLTF), no Draco package. See the Unity import guide. For Lightweight models, either is fine.

Unreal Engine

Use the FBX, the established route for meshes and skeletons. Unreal Engine 5 also has a built-in glTF importer, and since our GLBs carry no Draco compression, the GLB works there too.

Godot 4

The GLB, for every tier including rigged characters. Godot’s glTF importer can’t read Draco, which is exactly why our downloads skip it. The FBX works as well in Godot 4.3 and newer. Details in the Godot import guide.

Blender

The .blend opens directly with materials set up. If download size matters, the GLB is the smaller file for High Detail models (median 26.13 MB instead of 32.90 MB).

Web (three.js, model-viewer)

The GLB, ideally compressed for delivery: run gltf-transform with Draco or Meshopt on a copy, then add the DRACOLoader or the Meshopt decoder to three.js’s GLTFLoader (model-viewer decodes Draco out of the box). Keep in mind that the download is only half the story: a High Detail model with around 800,000 triangles and 4K textures is heavy on a phone. The light GLB halves the triangles, uses 1K textures and is a median 44 % of the download.

Apple AR (AR Quick Look)

The USDZ. For Lightweight models it is small (median 1.78 MB). High Detail USDZ files are a median 41.61 MB: fine on Wi-Fi, heavy on mobile data.

For the format basics behind these numbers, read glTF vs FBX vs OBJ. How the models and their files are produced is explained on how we make our models.

How to cite

Feel free to quote these numbers. Suggested citation: Grab3D, file sizes measured on 739 download packages, 30 Sep 2026, with a link to this page.