<!--
{
  "availability" : [
    "iOS: 26.0.0 -",
    "iPadOS: 26.0.0 -",
    "macCatalyst: 26.0.0 -",
    "macOS: 26.0.0 -",
    "tvOS: 26.0.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "AVFoundation",
  "identifier" : "/documentation/AVFoundation/AVCaptureSessionDeferredStartDelegate/sessionWillRunDeferredStart(_:)",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Method",
  "symbol" : {
    "kind" : "Instance Method",
    "modules" : [
      "AVFoundation"
    ],
    "preciseIdentifier" : "c:objc(pl)AVCaptureSessionDeferredStartDelegate(im)sessionWillRunDeferredStart:"
  },
  "title" : "sessionWillRunDeferredStart(_:)"
}
-->

# sessionWillRunDeferredStart(_:)

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

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

## Parameters

`session`

The [`AVCaptureSession`](/documentation/AVFoundation/AVCaptureSession) instance that runs the deferred start.

## 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`](/documentation/AVFoundation/AVCaptureSession/automaticallyRunsDeferredStart) property is set. See [`setDeferredStartDelegate(_:deferredStartDelegateCallbackQueue:)`](/documentation/AVFoundation/AVCaptureSession/setDeferredStartDelegate(_:deferredStartDelegateCallbackQueue:)) documentation for more information.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)