Glossary

USD (Universal Scene Description)

USD (Universal Scene Description) is Pixar's open-source 3D scene format, designed for combining geometry, materials, lighting and animation from many sources into a single, layered description of a 3D scene. Open-sourced in 2016, USD is now the backbone of major 3D pipelines including Apple's spatial computing stack and NVIDIA Omniverse. The familiar USDZ format is USD's binary, archived variant, used for distribution and as the iOS Augmented Reality format.

Quick Facts

Developer: Pixar Animation Studios
Open-sourced: 2016
License: Modified Apache 2.0
File extensions: .usd, .usda (ASCII), .usdc (binary), .usdz (archived)
Core feature: scene composition through layers and references
Major adopters: Pixar, Apple (RealityKit, visionOS), NVIDIA Omniverse, Autodesk
Web and AR relevance: USDZ variant is the iOS AR format

USD was built at Pixar for the demands of feature animation pipelines, where hundreds of artists across departments contribute to a single shot. The format’s defining trait is composition: a USD scene is a stack of layers (referenced sublayers, variants, payloads) that can be edited independently and combined deterministically. That makes USD ideal for collaborative 3D work, not just for shipping a single model.

USD comes in several file types. .usda is the human-readable ASCII form, useful for inspection and version control. .usdc is the binary form, smaller and faster to load. .usdz is a zip archive that packages USD content (geometry, textures, materials) into a single distributable file. That .usdz variant is what Apple Quick Look reads on iOS for AR.

Outside Pixar, USD has become the de facto standard for 3D scene exchange across animation, gaming, simulation and increasingly Apple’s spatial computing ecosystem. NVIDIA built Omniverse around USD as its native scene language. Apple uses USD throughout RealityKit and Reality Composer Pro, and USDZ is the iOS AR distribution format.

For day-to-day web and AR work, you mostly meet USD through its USDZ variant. Where USD shines is the larger pipeline: a 3D model authored in Reality Composer Pro or Blender can be exported as USD, edited and composed with other layers, and ultimately distributed as USDZ for iOS AR while a GLB derivative covers the rest of the web. That entire pipeline ends in PausAR Viewer on WordPress, which serves the right format to each device automatically.

Comparison

Extension	What it is	Typical use
.usda	USD in human-readable ASCII text	Inspection, version control, hand-editing
.usdc	USD in compact binary form	Day-to-day storage in pipelines
.usd	USD without specifying ASCII or binary	Generic reference, defaults vary by tool
.usdz	USD content packaged in a zip archive	Distribution, iOS AR via Apple Quick Look

FAQ

What's the difference between USD and USDZ?

USD is the underlying scene format, which can exist as multiple files. USDZ is the same content packaged in a single zip archive for distribution, and is what Apple Quick Look uses for iOS AR.

Do I need to author models in USD for Apple Vision Pro?

Not for a website. Standards-based GLB and USDZ work on Vision Pro through Safari and Quick Look. USD becomes relevant when you build native visionOS apps in Reality Composer Pro and RealityKit.

Where does USD fit in a typical web 3D workflow?

For the web you usually do not work with raw USD; you export GLB for the browser and USDZ for iOS AR. USD is the upstream format that those two derive from, particularly inside Apple-centric pipelines like Reality Composer Pro.