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How to convert GLB to USDZ for iPhone AR

Convert a GLB or glTF model to USDZ with Blender for free, so it opens in AR Quick Look on iPhone and iPad, and check what changed in the conversion.

Aman PorwalFounder @ Vi3W

3 min read

A ceramic teapot split down the middle: glazed teal on the left, grey clay with an even quad mesh grid on the right

Quick answer

How do I convert a GLB file to USDZ?

Import the GLB into Blender with File, Import, glTF 2.0, then export with File, Export, Universal Scene Description and give the file name a .usdz extension. Blender writes a zip package containing the USD and its textures. Then open the result in AR Quick Look on an iPhone to check the materials survived.

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Why you need both formats

Android and the web use GLB. Apple's AR Quick Look on iPhone and iPad uses USDZ. If you want a "view in your room" button that works on both, you need both files. Google's model-viewer then takes the GLB as src and the USDZ as ios-src. See embedding a 3D model.

Convert with Blender (free, any OS)

Blender is the most reliable free route, and it runs on Windows, macOS and Linux.

  1. Start clean. Open Blender, select the default cube, camera and light, and delete them.
  2. Import the GLB. Use File › Import › glTF 2.0 (.glb/.gltf).
  3. Check scale and orientation. glTF is in metres with +Y up, and Blender converts it on import. AR Quick Look shows the model at real size, so make sure a chair is chair-sized.
  4. Apply transforms. Select the model and press Ctrl+A › All Transforms.
  5. Export. Use File › Export › Universal Scene Description. Set the file name to end in .usdz. The Blender manual says this produces a zip package containing the USD and its texture files.

Check the result

Do not skip this. Conversions between material systems are rarely perfect.

  • On a Mac, open the USDZ in Preview and compare it with the GLB side by side. Preview reads both. See viewing 3D models on a Mac.
  • On an iPhone, AirDrop or message the file to yourself and open it in AR Quick Look. Check it at real size and under room lighting.

Things to look for:

  • Missing textures. Usually a texture Blender could not find on import. Re-import with the textures next to the file, or pack them into the .blend first.
  • Wrong colours or shine. Base colour, roughness, metallic and normal maps convert well. Exotic material features from glTF extensions may not survive.
  • Wrong size. Fix the scale in Blender and export again.

Other routes

  • Apple Reality Converter. Apple has offered this free Mac app for converting common 3D formats to USDZ. Availability and format support have varied between versions, so check Apple's developer site for the current release.
  • Apple's command-line USD tools suit batch conversion if you work in a pipeline.

Keep USDZ files light

AR runs on a phone, often over mobile data. Keep polygon counts modest and textures at 2048 pixels or smaller where you can. A cleanly retopologised model converts faster and loads faster.

Vi3W exports GLB with automatic retopology already applied, so the conversion above is the only step between a generated model and an iPhone AR link. The AR and VR use case covers the rest of that workflow.

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