---
title: "sessionWillRunDeferredStart(_:)"
framework: avfoundation
role: symbol
role_heading: Instance Method
path: "avfoundation/avcapturesessiondeferredstartdelegate/sessionwillrundeferredstart(_:)"
---

# sessionWillRunDeferredStart(_:)

This method gets called by the session when deferred start is about to run.

## Declaration

```swift
func sessionWillRunDeferredStart(_ session: AVCaptureSession)
```

## Parameters

- `session`: The doc://com.apple.avfoundation/documentation/AVFoundation/AVCaptureSession instance that runs the deferred start.

## Discussion

Discussion Delegates receive this message when the session has finished the deferred start. This message will be sent regardless of whether the session’s automaticallyRunsDeferredStart property is set. See setDeferredStartDelegate(_:deferredStartDelegateCallbackQueue:) documentation for more information.

## See Also

### Responding to deferred start events

- [sessionDidRunDeferredStart(_:)](avfoundation/avcapturesessiondeferredstartdelegate/sessiondidrundeferredstart(_:).md)