The read-only preferredReflectionFormat property of the XRSession interface returns this session's preferred reflection format used for lighting estimation texture data.

A string representing the reflection format. Possible values:

You can request a light probe with XRSession.requestLightProbe() and specify the system's preferred format by setting the reflectionFormat option equal to XRSession.preferredReflectionFormat.

const lightProbe = await xrSession.requestLightProbe({
  reflectionFormat: xrSession.preferredReflectionFormat,
});

• XRSession.requestLightProbe()