---
title: "findUnusedTrackID(completionHandler:)"
framework: avfoundation
role: symbol
role_heading: Instance Method
path: "avfoundation/avasset/findunusedtrackid(completionhandler:)"
---

# findUnusedTrackID(completionHandler:)

Loads an identifier that no other track in the asset uses.

## Declaration

```swift
func findUnusedTrackID(completionHandler: @escaping @Sendable (CMPersistentTrackID, (any Error)?) -> Void)
```

```swift
func findUnusedTrackID() async throws -> CMPersistentTrackID
```

## Parameters

- `completionHandler`: A completion handler the system calls after it finishes the request.

## See Also

### Loading tracks

- [tracks](avfoundation/avpartialasyncproperty/tracks-48zyw.md)
- [loadTrack(withTrackID:completionHandler:)](avfoundation/avasset/loadtrack(withtrackid:completionhandler:).md)
- [loadTracks(withMediaType:completionHandler:)](avfoundation/avasset/loadtracks(withmediatype:completionhandler:).md)
- [loadTracks(withMediaCharacteristic:completionHandler:)](avfoundation/avasset/loadtracks(withmediacharacteristic:completionhandler:).md)