---
title: optionalFeatures
framework: virtualization
role: symbol
role_heading: Instance Property
path: virtualization/vzcustomvirtiodeviceconfiguration/optionalfeatures
---

# optionalFeatures

The set of optional features that the device offers.

## Declaration

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

## Discussion

Discussion The optional features are the set of features that the guest driver may or may not accept, see negotiatedFeatures for the set of features that the guest accepts. A few feature bits are always set internally by default for optimal performance.