USDZ Spatial 3D Archive (Pixar / Apple VisionOS)
Zero-compression, 64-byte mmap-aligned PKZIP package created by Pixar & Apple for AR QuickLook and VisionOS spatial scenes, beginning with a root `.usdc` (`PXR-USDC`) or `.usda` stage.
Standard ZIP tools break USDZ! Every member MUST use `ZIP_STORED` (method 0) AND start its payload at an exact multiple of 64 bytes (padded via ZIP extra fields).
Drop any .usdz file (even 100 GB+) to inspect locally
Reads tiny File.slice() header/footer pages in a sandboxed Web Worker · 0 Bytes Uploaded
.usdz Magic Bytes & Header Offset Map
Uncompressed 64-byte aligned ZIP containing PXR-USDC layer at offset 0x40
| Byte Offset | Length | Data Type | Field Name | Engineering Description |
|---|---|---|---|---|
| 0x00 - 0x1D | 30 B | zip_lfh | local_header | ZIP header with compression_method == 0 (Store) |
| 0x1E - 0x3F | var | name+pad | alignment_pad | Filename + extra field padding to 64-byte boundary |
| 0x40 - 0x47 | 8 B | char[8] | usdc_magic | 'PXR-USDC' Crate binary stage header |
.usdz Security & Polyglot Risk Matrix
Verify method==0 (uncompressed), data_offset % 64 == 0 for every entry, and first entry extension in {.usdc, .usda, .usd}.
Read .usdz Header & Metadata Without Heavy Dependencies
import struct, sys
with open(sys.argv[1], "rb") as f:
hdr = f.read(30)
sig, ver, flags, method = struct.unpack("<IHHH", hdr[:10])
fn_len, ex_len = struct.unpack("<HH", hdr[26:30])
data_off = 30 + fn_len + ex_len
assert sig == 0x04034B50 and method == 0 and data_off % 64 == 0
print(f"Valid 64B-aligned USDZ: first data_offset=0x{data_off:X}")Deterministic .usdz Sample Files & Edge Cases
minimal-64b-aligned.usdz
Apple VisionOS / QuickLook compliant uncompressed ZIP with 64-byte mmap alignment and `PXR-USDC` Crate root layer.
curl -fsSL https://fileformat.co/fixtures/v1/usdz/minimal-64b-aligned.usdz -o minimal-64b-aligned.usdz \
&& echo "84ed4c279742f4c9aa8557034806427c40d29fb91d3415def454b5371035f3bf minimal-64b-aligned.usdz" | shasum -a 256 -cspatial-stage-textured.usdz
64-byte aligned USDZ archive bundling both a `PXR-USDC` binary stage and an uncompressed RGBA PNG texture.
curl -fsSL https://fileformat.co/fixtures/v1/usdz/spatial-stage-textured.usdz -o spatial-stage-textured.usdz \
&& echo "30477e3f8aaf315b7f84c5950a266a44d86d615dd8ad087d49825eb2b6a35f1e spatial-stage-textured.usdz" | shasum -a 256 -cunaligned-violation.usdz
Valid ZIP containing `scene.usdc`, but entry data starts at non-64B-aligned offset—catches subtle USDZ packager bugs.
curl -fsSL https://fileformat.co/fixtures/v1/usdz/unaligned-violation.usdz -o unaligned-violation.usdz \
&& echo "1b5d09db530a3b47b91227c552a243fc0a0debb7e2e757ad2d6988a07e86cdae unaligned-violation.usdz" | shasum -a 256 -cRelated Specifications & Alternatives
Khronos Group's single-file binary 3D delivery format combining a 12-byte header, a UTF-8 JSON scene-graph chunk (`0x4E4F534A`), and a raw GPU geometry/texture buffer (`0x004E4942`).
ZIP-compressed iOS/iPadOS application distribution archive structured around `Payload/<AppName>.app/Info.plist` (`bplist00`) and Mach-O ARM64 binaries.
Lossless CRC-checked chunked raster image format, heavily used in AI workflows (ComfyUI / Stable Diffusion) to store generation graphs and prompts inside `tEXt`/`iTXt` chunks.