---
title: userDefinedAncillaryDataSizeRemaining
framework: AVFoundation
role: symbol
role_heading: Instance Property
platforms: [iOS 27.0+, iPadOS 27.0+, Mac Catalyst 27.0+, macOS 27.0+, tvOS 27.0+]
path: avfoundation/avcaptureancillarydataencoder/userdefinedancillarydatasizeremaining
---

# userDefinedAncillaryDataSizeRemaining

Allows users to track how much data in bytes can be added to the userDefinedAncillaryData.

## Declaration

```swift
var userDefinedAncillaryDataSizeRemaining: Int16 { get }
```

## Discussion

Discussion Using SMPTE 291 and SMPTE RDD 18 standards for ancillary data, this property specifies max size in bytes for the user defined portion of that data