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What are .usdz and .usd files? The USD 3D format, and how to open it on a Mac

USD (Universal Scene Description) is Pixar's open format for 3D scenes, and USDZ is its packaged form, which Apple uses for AR on iPhone, iPad and Vision Pro. A scene can be stored as text (.usda), in binary (.usdc) or either way (.usd), and it can be made of many files. A Mac knows it better than almost any other 3D format: on macOS 27, Preview opens it, edits it and saves it.

At a glance

Extension
.usdz, .usd, .usda, .usdc
Type
3D scene
Created by
Pixar
Since
2016
Standard
Not a formal standard
Specification
OpenUSD: USDZ
macOS without an app
Opens it and shows previews

Facts checked November 4, 2026

Four extensions, one format

  • .usda is readable text and starts with the line #usda 1.0.
  • .usdc is the binary encoding called Crate. It starts with the bytes PXR-USDC and loads faster.
  • .usd can be either; a program tells them apart when it opens the file.
  • .usdz is an uncompressed ZIP holding the scene together with its textures. The files inside are aligned to 64 bytes so they can be read straight from memory, and the first file must be a USD scene.

On macOS 27, tools for USD come with the system, in /usr/bin. usdcat prints a binary file as text, usdtree shows the scene's structure, usdzip packs a USDZ and usdchecker checks it. This is how a cylinder exported from Blender as .usdc starts, printed as text by usdcat:

#usda 1.0
(
    defaultPrim = "root"
    doc = "Blender v5.1.0"
    metersPerUnit = 1
    upAxis = "Z"
)

And this is its scene according to usdtree. Besides the cylinder, there are lights and a camera:

/
 `--root [def Xform]
     |--Light [def Xform]
     |   `--Light [def SphereLight]
     |--cylinder [def Xform]
     |   `--cylinder [def Mesh] (active = true)
     |--Camera [def Xform]
     |   `--Camera [def Camera]
     `--env_light [def DomeLight]

A scene made of many files

USD can build a scene from several files: layers, references to other files, variants, textures next to the scene. For a studio with thousands of objects that's a strength; for someone who got one file, it's a trap. Apple's Preview guide explicitly advises against moving USD files out of their folder.

When I packed our cylinder into a USDZ with usdzip, usdchecker rejected the package. The scene refers to a texture, textures/color_0C0C0C.exr, that isn't in the package, because I packed only the .usdc. Before you send a USDZ on, have it checked:

usdchecker model.usdz

For sharing, USDZ is the right choice, because it carries everything in one file. It does have to actually contain everything, though.

Units: metersPerUnit and the up axis

USD writes its unit into the scene header as metersPerUnit: how many metres one unit is. If it's missing, centimetres apply (0.01). The header also states which axis points up, upAxis Y or Z, and programs don't agree on it.

The Blender cylinder above has metersPerUnit = 1 in its header – metres – but its extent in the file runs from −27 to 27. According to the file, it's a cylinder 54 metres wide. The numbers were really millimetres, and the header says otherwise. On macOS 27, Preview lets you change a scene's units and up axis.

What USD carries

  • Meshes and other geometry, with an object hierarchy and names.
  • Materials and textures. A USDZ can hold PNG, JPEG, EXR and AVIF images.
  • Lights and cameras, as the tree above shows.
  • Animation. Preview on macOS 27 can play it.

Where USD came from

Pixar started developing USD in 2012 as the successor to its earlier scene systems and released it as open source in July 2016. Apple introduced USDZ together with Pixar at WWDC in June 2018, for AR Quick Look in iOS 12. In August 2023 Pixar, Adobe, Apple, Autodesk and NVIDIA founded the Alliance for OpenUSD, and in December 2025 it published its first normative specification, OpenUSD Core Specification 1.0. The alliance calls it a first step toward an ISO standard.

How to open USD and USDZ on a Mac, iPad, iPhone and Vision Pro

USD is one of the few 3D formats Apple supports fully:

  • On a Mac, Preview opens it on macOS 27. You can move and rotate parts, change materials and lights, switch between three renderers, and save to USD, USDA, USDC or USDZ. It edits a single-layer file directly and saves others as a copy. Quick Look and the Finder show USD, USDA, USDC and USDZ by themselves (checked on macOS 27.0.1). One report on Apple's forums says some USDZ files rendered black in Preview on macOS 26.2.
  • On iPhone and iPad, AR Quick Look opens USDZ straight from Files, Safari, Messages, Mail or Notes, from iOS 12 on.
  • On Vision Pro, Quick Look shows it in your space.
  • Reality Composer Pro from Apple is for creating AR scenes.

Preview3D opens USD, USDA, USDC and USDZ on Mac, iPad, iPhone and Vision Pro, with the materials and lights the file has. It adds what Preview doesn't: Model info with the dimensions and triangle count, a mesh check, and conversion to formats for printing.

Converting USDZ to STL

Preview saves 3D only to USD formats. For printing you need STL, OBJ or PLY, and Preview3D converts to those on a Mac from File → Export model as… (⌥⌘E), without uploading anything. Materials, lights and animation are dropped. Check the size in the slicer afterwards, because USD can be in centimetres, metres or anything else – and the header doesn't have to match reality, as the cylinder above shows.

Common questions

What's the difference between .usda, .usdc and .usdz?

.usda is text, .usdc is binary, and .usd can be either. .usdz is a ZIP package with the scene and its textures in one file.

Which one should I send?

USDZ. It's one file, and iPhone, iPad, Vision Pro and Mac open it without another app.

Why did my USD lose its textures after I moved it?

A USD scene often refers to files in its folder. Move the whole folder, or pack the scene into a USDZ and check it with usdchecker.

Can I edit a USDZ?

By the specification the package is read-only: unpack, edit, repack. Preview on macOS 27 edits a single-layer scene directly and saves others as a copy.

How do I convert USDZ to STL?

On a Mac, in Preview3D with File → Export model as…, without uploading it anywhere. Then check the size in the slicer.

Does Android open USDZ?

No. On Android and the web, GLB is used instead.

Related pages

Sources

Have a USDZ from your iPhone – a scan, say – and don't know how to measure or print it? Write to me at apps@xfanta.com and I'll take a look.

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