---
title: "setRDD18AncillaryDataString(_:forTag:)"
framework: AVFoundation
role: symbol
role_heading: Instance Method
platforms: [iOS 27.0+, iPadOS 27.0+, Mac Catalyst 27.0+, macOS 27.0+, tvOS 27.0+]
path: "avfoundation/avcaptureancillarydataencoder/setrdd18ancillarydatastring(_:fortag:)"
---

# setRDD18AncillaryDataString(_:forTag:)

Allows the user to add their own string to be encoded as data and transmitted using SMPTE RDD 18 standards.

## Declaration

```swift
func setRDD18AncillaryDataString(_ string: String, forTag tag: UInt16) throws
```

## Parameters

- `string`: The string to be encoded as data and transmitted
- `tag`: The SMPTE RDD 18 tag with value between 0xE011 and 0xFFFF or valid tags definded in SMPTE RDD 18:2021