Using Custom Masking for Session Replay

By default, our Session Replay SDK masks all text content, images, and user input. This helps ensure that no sensitive data will be exposed. You can also manually choose which parts of your app's data you want to mask by using the different options listed below.

Mask by View Class

You can choose which type of view you want to mask or unmask by using the maskedViewClasses or unmaskedViewClasses options.

Let's say you have a custom view that you want to mask and a UILabel subclass (which normally would be masked) that you don't want to mask. You can set the options like this:

options.sessionReplay.maskedViewClasses = [MyCustomView.self]
options.sessionReplay.unmaskedViewClasses = [MyCustomLabel.self]

Mask by View Instance

You can also choose to mask or unmask a specific view instance by using the replay API (SentrySDK.replay) or view extensions like this:

SentrySDK.replay.maskView(view: view)
SentrySDK.replay.unmaskView(view: label)

or

view.sentryReplayMask()
label.sentryReplayUnmask()

SwiftUI

Because of the way SwiftUI is transformed into UIKit, it will often be over-masked. A modifier like background uses the same element as an Image. In order to control the SwiftUI masking process, you need to use the sentryReplayUnmask and/or sentryReplayMask modifiers.

In this example we want to show the message, but not the user name.

@Binding var user: String

var body: some View {
  VStack {
    Text("Hello")
      .sentryReplayUnmask()
    Text("\(user)")
  }
}

In this example, we need to unmask the VStack because its background element will be masked by default. To hide the username, we need to mask it.

@Binding var user: String

var body: some View {
  VStack {
    Text("Hello")
    Text("\(user)")
      .sentryReplayMask()
  }
  .background(.blue)
  .sentryReplayUnmask()
}

Ignore View Types from Subtree Traversal

Some view hierarchies contain layers that crash when accessed during traversal. For example, CameraUI.ChromeSwiftUIView on iOS 26+ contains CameraUI.ModeLoupeLayer instances that cause fatal errors when their sublayers property is accessed, resulting in crashes during session replay or screenshot capture.

To prevent these crashes, you can configure the SDK to skip traversing the subtree of specific view types while still redacting the view itself if needed.

Default Behavior

On iOS 26+, CameraUI.ChromeSwiftUIView is automatically included in the ignore set by default to prevent crashes. On other platforms or iOS versions, the ignore set is empty by default.

Adding View Types to Ignore List

You can add custom view types to the ignore set using the excludeViewTypeFromSubtreeTraversal method:

options.sessionReplay.excludeViewTypeFromSubtreeTraversal("MyProblematicView")

The view type identifier uses partial string matching against the result of type(of: view).description(). This means if you exclude "MyView", it will match "MyApp.MyView", "MyViewSubclass", "Some.MyView.Container", etc. The view type identifier typically follows the format "ModuleName.ClassName".

Removing View Types from Ignore List

If you need to remove a view type from the ignore set (not recommended for default values), you can use:

options.sessionReplay.includeViewTypeInSubtreeTraversal("CameraUI.ChromeSwiftUIView")

The view type identifier uses exact string matching against the result of type(of: view).description(). This means "MyApp.MyView" will only match exactly "MyApp.MyView", not "MyApp.MyViewSubclass". This exact matching prevents accidental matches when removing view types from the ignore set.

Dictionary Initialization

You can also configure ignored view types when initializing SentryReplayOptions from a dictionary:

let replayOptions = SentryReplayOptions(dictionary: [
    "excludedViewClasses": ["MyCustomView", "AnotherProblematicView"],
    "includedViewClasses": ["CameraUI.ChromeSwiftUIView"]
])

• excludedViewClasses: An array of view type identifier patterns that use partial matching (contains)
• includedViewClasses: An array of view type identifiers that use exact matching to remove items from the excluded set

How It Works

The final set of excluded view types is computed using the formula: Default View Classes + Excluded View Classes - Included View Classes

• Default view classes are defined internally by the SDK (e.g., CameraUI.ChromeSwiftUIView on iOS 26+)
• Excluded view classes use partial matching (contains) - if a view's class name contains the pattern, it's excluded
• Included view classes use exact matching - they remove specific view types from the excluded set

When a view type is ignored from subtree traversal:

• The view itself is still redacted (unless it's explicitly marked to be ignored, like UISwitch)
• The SDK skips traversing the view's subtree, preventing crashes from accessing problematic sublayers
• This prevents crashes while maintaining privacy protection for the view itself

Debugging Session Replay masking

To see how elements are being masked, enable the masking preview from anywhere in your app. It will display an overlay on top of the masked elements. This works on the simulator and on device, as well as within Xcode Preview.

SentrySDK.replay.showMaskPreview()

By default, the overlay will be opaque. To configure the opacity, pass the desired opacity as a parameter:

SentrySDK.replay.showMaskPreview(0.5) // 0.5 opacity to render the preview semi-transparent

Make sure not accidentally include this in your release build by e.g. wrapping it in a #if DEBUG block.

#if DEBUG
  SentrySDK.replay.showMaskPreview()
#endif

To preview masking during the design phase of your SwiftUI views, use the sentryReplayPreviewMask modifier.

This view modifier works on the simulator and on device, as well as within Xcode Preview. Therefore we recommend to apply the modifier only in your preview code, to ensure proper masking without affecting the final release build.

Note that when you apply this modifier to a view, it will show the masking preview for the entire window containing that view, not just the view itself.

struct ContentView_Previews: PreviewProvider {
  static var previews: some View {
    ContentView()
      .sentryReplayPreviewMask()
  }
}