---
title: "estimateOutputFileLength(completionHandler:)"
framework: avfoundation
role: symbol
role_heading: Instance Method
path: "avfoundation/avassetexportsession/estimateoutputfilelength(completionhandler:)"
---

# estimateOutputFileLength(completionHandler:)

Starts estimating the output file length of the export while considering the asset, preset, and time range configuration of the export session.

## Declaration

```swift
func estimateOutputFileLength(completionHandler handler: @escaping @Sendable (Int64, (any Error)?) -> Void)
```

```swift
var estimatedOutputFileLengthInBytes: Int64 { get async throws }
```

## Parameters

- `handler`: A callback the system invokes when it finishes its estimation. It passes the callback the following parameters:

## See Also

### Estimating file length and duration

- [estimatedOutputFileLength](avfoundation/avassetexportsession/estimatedoutputfilelength.md)