Implement Session Replay (iOS)

Overview

This developer guide will assist you in configuring your Swift app for Session Replay using the Session Replay SDK (Swift). Learn more about viewing captured Replays in your project here.

Prerequisite

You are already a Mixpanel customer and have the latest version of the Mixpanel Swift SDK installed (minimum supported version is v4.3.1). If not, please follow this doc to install the SDK.

Installation

To capture Session Replays in your app, add the Session Replay SDK using Swift Package Manager directly in Xcode:

1. In Xcode, go to File → Add Package Dependencies…
2. Paste the GitHub URL: https://github.com/mixpanel/mixpanel-ios-session-replay-package
3. Follow the prompts to select the latest version and add the package to your project.

Initialize

You should have the main Mixpanel Swift SDK installed (minimum version v4.3.1), if not, please refer to Prerequisite.

Add the following code to your SwiftUI or UIKit app.

SwiftUI

import Mixpanel
import MixpanelSessionReplay
 
struct SessionReplayDemoApp: App {
    @State private var isActive = true
    @Environment(\\.scenePhase) private var scenePhase
 
    var body: some Scene {
        WindowGroup {
            ...
        }
        .onChange(of: scenePhase) {
            if scenePhase == .active {
                let config = MPSessionReplayConfig(wifiOnly: false, enableLogging: true)
                MPSessionReplay.initialize(
                        token: Mixpanel.mainInstance().apiToken,
                        distinctId: Mixpanel.mainInstance().distinctId,
                        config: config
                )
            }
        }
}

UIKit

import Foundation
import UIKit
 
import Mixpanel
import MixpanelSessionReplay
 
class AppDelegate: UIResponder, UIApplicationDelegate {
 
    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? = nil) -> Bool {
        Mixpanel.initialize(token: token, trackAutomaticEvents: true)
        Mixpanel.mainInstance().loggingEnabled = true
 
        let config = MPSessionReplayConfig(wifiOnly: false, enableLogging: true)
        MPSessionReplay.initialize(
                token: Mixpanel.mainInstance().apiToken,
                distinctId: Mixpanel.mainInstance().distinctId,
                config: config
        )
    }
}

Capturing Replays

You can capture replay data using a sampling method (recommended), or customize when and where replays are captured manually using methods provided by the Session Replay Swift SDK.

Sampling

We recommend using our sampling functionality unless you need custom logic to decide when to record sessions.

To enable Session Replay and set your sampling rate, create a MPSessionReplayConfig object and set the autoStartRecordingSessionsPercent with a value between 0.0 and 100.0. At 0.0 no sessions will be recorded, at 100.0 (default) all sessions will be recorded.

Start with a low sampling rate, then adjust according to your specific analytics needs.

Upon initialization, recording starts automatically if the sampling check passes.

Example Usage

// records 1% of all sessions
MPSessionReplayConfig(autoStartRecordingSessionsPercent: 1.0)

Manual Recording

To programatically start and stop replay capture, use the .startRecording() and .stopRecording() methods.

Start Recording Replay Data

Calling .startRecording() will force recording to begin regardless of the autoStartRecordingSessionsPercent sampling check.

Recording automatically stops when the app goes into the background. If autoStartRecording is true (default) recording automatically re-starts when the app comes back to the foreground.

Calling .startRecording() has no effect while recording is already in progress. Example Usage

// manually force recording to begin for 100% of sessions
MPSessionReplay.getInstance()?.startRecording()

// manually force recording to begin with a 50% sampling rate
MPSessionReplay.getInstance()?.startRecording(recordSessionsPercent: 50.0)

Stop Recording Replay Data

Call .stopRecording() to stop any active replay data collection. The SDK automatically stops recording when the app goes to the background.

Calling .stopRecording() has no effect when there is no recording in progress.

Example Usage

// manually end a replay capture
MPSessionReplay.getInstance()?.stopRecording()

Manual Screenshot Capture

You can also manually trigger the capture of individual screenshots by calling .captureScreenshot():

Example Usage

// manually capture screenshots
MPSessionReplay.getInstance()?.captureScreenshot()
 
// manually capture screenshots triggered by a touch event
MPSessionReplay.getInstance()?.captureScreenshot(withTouchEvent: touchEvent)

Example Use Cases for Manual Capture

Additional Configuration Options

Upon initialization you can provide a MPSessionReplayConfig object to customize your replay capture.

Currently, there are six config options:

autoMaskedViews Example Usage

// mask images only
MPSessionReplayConfig(autoMaskedViews: [.image])
 
// disable auto masking
MPSessionReplayConfig(autoMaskedViews: [])

Alternatively:

// mask images only
MPSessionReplay.getInstance()?.autoMaskedViews = [.image]
 
// disable auto masking
MPSessionReplay.getInstance()?.autoMaskedViews = []

Identity Management

The Mixpanel distinct ID for the current user can be passed into the initializer and changed at runtime by calling the .identify(distinctId:) method:

Example Usage

// initialize the main Mixpanel tracking SDK
Mixpanel.initialize(token: token, trackAutomaticEvents: true)
 
// initialize the session replay SDK with the project token and distinct ID from above
MPSessionReplay.initialize(
        token: Mixpanel.mainInstance().apiToken,
        distinctId: Mixpanel.mainInstance().distinctId,
)

To change the distinct ID later:

// for example when the user logs out
func logout() {
    // reset the main Mixpanel tracking SDK to generate a new distinct ID
    Mixpanel.mainInstance().reset()
    let newDistinctId = Mixpanel.mainInstance().getDistinctId()
    // change session replay distinct ID
    MPSessionReplay.getInstance()?.identify(distinctId: newDistinctId)
}

Manual Flushing

You can flush any currently queued session replay events at any time by calling .flush():

MPSessionReplay.getInstance()?.flush()

Replay ID

When a replay capture begins, a Replay ID is generated by the SDK and is attached as an event property ($mp_replay_id) to events tracked by the Mixpanel SDK during the capture session. Events containing the same $mp_replay_id will appear in the same Replay.

If you are sending any events not coming from the Mixpanel SDK, add the $mp_replay_id event property to attribute the event to a specific Replay.

You can use the getReplayId() method to return the Replay ID for the current replay capture. The method will return an empty object if there is no active replay capture in progress.

Example Usage

// return the $mp_replay_id for the currently active capture
MPSessionReplay.getInstance()?.getReplayId()
// {$mp_replay_id: '19221397401184-063a51e0c3d58d-17525637-1d73c0-1919139740f185'}

Server-Side Stitching

Server-Side Stitching allows you to easily watch Replays for events that were not fired from the SDK.

It works by inferring the Replay that an event belong using the Distinct ID and time property attached to the event. This is especially useful if you have events coming in from multiple sources.

For example, let’s say a user with Distinct ID “ABC” has a Replay recorded from 1-2pm. Two hours later, an event was sent from your warehouse with a timestamp of 1:35pm with Distinct ID “ABC”. Server-Side Stitching will infer that the event should belong in the same Replay.

To ensure Server-Side Stitching works, call identify() from the client-side using our SDK with the user’s $user_id. This guarantees that events generated from both the client-side and server-side share the same Distinct ID. Learn more about identifying users.

Debugging

When a Replay capture begins, a “Session Recording Checkpoint” event will appear in your project, tracked as $mp_session_record. You may use this event to verify whether you have implemented Session Replay correctly.

If you are using the recommended sampling method to capture your Replays but having trouble finding the Replays in your project, try calling .startRecording() manually and see if the $mp_session_record event appears. If it does appear but you are still struggling to locate your Replays, you may want to increase your sampling rate.

You can also check the Home page for your project to check for any recent Replays listed in the “Latest Replays” card.

If you are still struggling to implement, submit a request to our Support team for more assistance.

Logging

Developers can enable or disable logging with the enableLogging option of the MPSessionReplayConfig object or via the loggingEnabled property of the main MPSessionReplay instance.

Example Usage

let token = Mixpanel.mainInstance().apiToken
let distinctId = Mixpanel.mainInstance().distinctId
let config = MPSessionReplayConfig(wifiOnly: false, enableLogging: true) // enable debug logging
MPSessionReplay.initialize(token: token, distinctId: distinctId, config: config)

Alternatively:

MPSessionReplay.getInstance()?.loggingEnabled = true

Privacy

Mixpanel offers a privacy-first approach to Session Replay, including features such as data masking. Mixpanel’s Session Replay privacy controls were designed to assist customers in protecting end user privacy. Read more here.

User Data

The Mixpanel SDK will always mask all input text fields. To protect end-user privacy, input text fields cannot be unmasked.

By default, all text, images, WKWebViews and MKMapViews are also masked.

You can unmask these elements at your own discretion using the autoMaskedViews config option described above.

Mark Views as Sensitive

If your app is SwiftUI-based or UIKit-based, all UITextField and UILabel components are masked by default. UITextField cannot be unmasked, while UILabels can be unmasked

You can also mark any views as sensitive using mpReplaySensitive. Views marked as “sensitive” will always be masked.

Example Usage

// Mark any view as sensitive
 
// SwiftUI
Image("family photo")
	.mpReplaySensitive(true)
 
// UIKit
let ccView = CreditCardUIView()
ccView.mpReplaySensitive = true

Set mpReplaySensitive to false to mark any view as “safe”. Views marked as “safe” will never be masked.

Example Usage

// Mark any view as safe
 
// SwiftUI
BackgroundImage()
    .mpReplaySensitive(false)
 
//UIKit
let bgImage = BackgroundImage()
bgImage.mpReplaySensitive = false

Retention

By default, Mixpanel retains Session Replays for 30 days from the date the replay is ingested and becomes available for viewing within Mixpanel. Customers on our Enterprise plan can customize this retention period between 7 days and 360 days. Once a replay is expired, there is no way to view that replay.

Legal (Beta Terms)

Our Session Replay Beta Service Addendum can be found here.

The alpha and beta of Mixpanel’s mobile session replay SDK will track certain events and send them to Mixpanel so that Mixpanel can understand and improve the alpha and beta mobile session replay feature experience. These events include starting and stopping a session, adding and removing sensitive classes, adding sensitive views and adding safe views. Nothing about your application will be included in this tracking; only your usage of the Mixpanel Session Replay SDK.

FAQ

How does Session Replay work in iOS?

Session Replay observes user interactions within your app, capturing UI hierarchy changes and storing them as images, which are then sent to Mixpanel. Mixpanel reconstructs these images, applying recorded events as an end-user completes them.

Within Mixpanel’s platform, you can view a reconstruction of your end-user’s screen as they navigate your app.

However, Session Replay is not a literal video recording of your end-user’s screen; end-user actions are not video-recorded.

Can I prevent Session Replay from recording sensitive content?

The Mixpanel SDK will always mask all inputs. By default, all text, images, and WebViews on a page.

Additionally, you can customize how you leverage our SDK to fully control (1) where to record and (2) whom to record. Consider the manual capture example scenarios, SDK configuration options, and manual view masking example provided above to customize the replay capture of your implementation.

How can I estimate how many Replays I will generate?

If you already use Mixpanel, the Session Start events are a way to estimate the rough amount of replays you might expect. This is especially true if you use timeout-based query sessions. However, because our sessions are defined at query time, we cannot guarantee these metrics will be directly correlated.

When you enable Session Replay, use the above proxy metric to determine a starting sampling percentage, which will determine how many replays will be sent. You can always adjust this as you go to calibrate to the right level.

How does Session Replay affect my app’s performance?

There is no impact on your app’s performance when there are no user interactions or nothing changes on the screen. When there are user interactions, we expect negligible impact on CPU usage and memory consumption. There is no impact on disk I/O because Session Replay does not write anything to your disk.

In our own testing, the overhead is unnoticeable, however this testing was not exhaustive, and you may discover the recording overhead may negatively impact your mobile application performance depending on your application specifications. If you experience any performance degradations after installing Session Replay, please reach out to our Support team.

How Does Session Replay affect my app’s bandwidth consumption?

The bandwidth impact of Session Replay depends on the setting of the wifiOnly parameter.

By default, wifiOnly is set to true, which means replay events are only flushed to the server when the device has a wifi connection. If there is no wifi, flushes are skipped, and the events remain in the in-memory queue until WiFi is restored. This ensures no additional cellular data is used, preventing users from incurring additional data charges.

When wifiOnly is set to false, replay events are flushed with any available network connection, including cellular. In this case, the amount of cellular data consumed depends on the intensity of user interactions and the typical session length of your app. Users may incur additional data charges if large amounts of data are transmitted over cellular connections.

How does Session Replay for mobile work if my app is offline?

Session Replay for mobile does not work in offline mode.

Does it work in SwiftUI/UIKit apps?

Yes.

Does it support Obj-C based app?

Yes, Objective-C and Swift are fully interoperable.

Does Mobile Session Replay work with my CDP?

Yes — but only if the Mixpanel Session Replay SDK is installed client-side.

Mobile Session Replay is compatible with CDPs like Segment and mParticle, but you must integrate the Mixpanel Session Replay SDK directly in your mobile app. Without it, replays won’t be captured.

Key Considerations:

• If you’re using Segment server-side, session replays will not be recorded, since the SDK isn’t running in the app.
• For Segment’s client-side Analytics-Swift SDK, you can use Segment’s Plugin Architecture to enrich events with the $mp_replay_id property, ensuring they’re linked to their replays.
• The Mixpanel Session Replay SDK is separate from the standard Mixpanel tracking SDK. You do not need the regular SDK, but the Replay SDK must be configured with a distinct_id and project token.
• Events can be linked to replays either by:
  • Manually attaching the current replay ID to each event
  • Using server-side stitching after the fact