How do I catch this when it only happens for some players?

Capture it automatically from the player's device with the full stack trace, the device and OS, the build, and a breadcrumb trail of what they did. That turns a vague complaint into a specific, reproducible issue you can fix without owning the hardware it happens on.

How to Fix an AR Object Appearing at the Wrong Real-World Scale in Unity AR Foundation

Q: What causes an AR object appearing at the wrong real-world scale in Unity AR Foundation?

The model's import scale or content-placement scale does not match the AR session's one-unit-equals-one-meter convention, so it looks oversized or tiny.

Quick answer: Author the model so one Unity unit equals one meter, fix the FBX import scale, and avoid scaling the AR Session Origin to fake size.

AR Foundation places the virtual world at real-world scale where one unit is one meter. A model imported at the wrong scale, or a parent rescaled to compensate, will look wrong next to real objects. Getting the asset to true metric scale makes placement match reality.

How to fix it

1. Use metric units

Author or import the model so one Unity unit equals one meter; fix the FBX Scale Factor instead of scaling the instance at runtime.

2. Do not rescale the session origin

Avoid scaling the AR Session Origin or XR Origin to fake size, since that distorts hit tests and anchors as well.

3. Validate against a known object

Place a one-meter reference cube to confirm scale, then adjust the model's own scale to match real measurements.

Catching the ones you can't reproduce

The hardest version of this to fix is the one you can't reproduce — it only happens on a player's hardware, OS, driver, or save state, under conditions that simply aren't present on your machine. A report that says “it crashed” or “it froze” gives you nothing to act on, so the bug survives release after release while quietly costing you players.

Automatic error capture closes that gap. Each failure arrives with its full stack trace, the device and OS, the build number, and a breadcrumb trail of what the player did right before it broke, so even a failure you have never seen becomes a specific, reproducible issue. Fold identical failures into one signature ranked by how many players each hits, and your worklist sorts itself worst-first instead of arriving as a stream of vague complaints.

This is where a tool like Bugnet earns its place. Its SDK captures every mobile error automatically with the full stack trace plus device, OS, memory, build, and game-state context, folds duplicates into one grouped issue with an occurrence count, and ties each to the build it first appeared on — so you fix the problem that hurts the most players first and confirm it is gone when its signature disappears from the next release.

Ship the fix, watch the signature disappear from the next build. That's how you know it's really gone.