A USDZ file is a zip archive containing the scene, textures and materials in USD form. Safari recognises it and opens AR Quick Look directly.
Because web viewers use glTF/GLB, an AR-ready product needs both: Thridify exports USDZ automatically from the same source model so iOS shoppers get the same product in AR.
How USDZ is put together
Apple and Pixar introduced USDZ in 2018. It is a zip archive with no compression and a fixed byte alignment, so iOS can read the files inside without unpacking them. That is why a USDZ cannot be made with an ordinary zip tool: a file that looks right can still refuse to open.
Inside are a USD scene and its textures, usually PNG or JPEG. Apple’s Reality Converter and the usdzconvert tools produce valid files, and most 3D pipelines that serve AR generate USDZ from the same source as their GLB.
Why USDZ files are often larger than GLB
The web compression tricks that keep GLB small, Draco for geometry and KTX2 for textures, are glTF extensions. USDZ does not use them, so the iOS file for the same product is often several times the size of the Android one. Sensible texture sizes matter more for USDZ than anywhere else.
Details that change the iPhone experience
A Quick Look link can carry options after a # in the URL. allowsContentScaling=0 stops the shopper pinching the product to the wrong size, which matters when the point of AR is checking fit. Quick Look can also show a banner with a title and a call to action.
Materials should use the standard physically based inputs (base colour, metallic, roughness, normal). Anything that depends on a custom shader in the web viewer has to be baked into textures before it will show on iPhone.
Why it matters
Without USDZ there is no app-free AR on iPhone — roughly half of many brands’ mobile traffic.
Questions about USDZ
- Does Android support USDZ?
- Not for AR. Android’s Scene Viewer uses glTF or GLB. Serve USDZ to iOS and GLB to everyone else.
- Can I convert GLB to USDZ?
- Yes. Apple’s Reality Converter and several open tools convert GLB to USDZ. Check the result on a real iPhone, because unsupported materials fall back silently.
- Why does my USDZ open as a blank file?
- Usually the archive was re-zipped with compression or the wrong alignment, or the server sends it with the wrong content type. Serve it as model/vnd.usdz+zip.