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# optionalFeatures

The set of optional features that the device offers.

```
var optionalFeatures: VZVirtioFeatureSet { get }
```

## Discussion

The optional features are the set of features that the guest driver may or may not accept, see
[`negotiatedFeatures`](/documentation/Virtualization/VZCustomVirtioDevice/negotiatedFeatures) for the set of features that the guest accepts. A few feature bits are always set
internally by default for optimal performance.

---

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