diff --git a/example/src/main/java/com/example/MainActivity.java b/example/src/main/java/com/example/MainActivity.java
index 89ecbca5..10003620 100644
--- a/example/src/main/java/com/example/MainActivity.java
+++ b/example/src/main/java/com/example/MainActivity.java
@@ -4,10 +4,13 @@
 import android.os.Bundle;
 import android.os.Handler;
 import android.os.Message;
+import android.text.Editable;
 import android.view.View;
+import android.widget.EditText;
 import android.widget.TextView;
 
 import com.parsely.parselyandroid.ParselyTracker;
+import com.parsely.parselyandroid.SiteIdSource;
 import com.parsely.parselyandroid.ParselyTrackerInternal;
 import com.parsely.parselyandroid.ParselyVideoMetadata;
 
@@ -23,6 +26,7 @@
  */
 public class MainActivity extends Activity {
 
+    public static final String DEFAULT_SITE_ID = "example.com";
     private InternalDebugOnlyData internalDebugOnlyData;
 
     @Override
@@ -31,7 +35,7 @@ protected void onCreate(Bundle savedInstanceState) {
         setContentView(R.layout.activity_main);
 
         // initialize the Parsely tracker with your site id and the current Context
-        ParselyTracker.init("example.com", 30, this, true);
+        ParselyTracker.init(DEFAULT_SITE_ID, 30, this, true);
         internalDebugOnlyData = new InternalDebugOnlyData((ParselyTrackerInternal) ParselyTracker.sharedInstance());
 
         final TextView intervalView = (TextView) findViewById(R.id.interval);
@@ -96,14 +100,14 @@ public void trackPageview(View view) {
         //       the post has an internet-accessible URL, we will crawl it. urlMetadata is only used
         //       in the case of app-only content that we can't crawl.
         ParselyTracker.sharedInstance().trackPageview(
-                "http://example.com/article1.html", "http://example.com/", null, null
+                "http://example.com/article1.html", "http://example.com/", null, null, getSiteId()
         );
     }
 
     public void startEngagement(View view) {
         final Map<String, Object> extraData = new HashMap<>();
         extraData.put("product-id", "12345");
-        ParselyTracker.sharedInstance().startEngagement("http://example.com/article1.html", "http://example.com/", extraData);
+        ParselyTracker.sharedInstance().startEngagement("http://example.com/article1.html", "http://example.com/", extraData, getSiteId());
         updateEngagementStrings();
     }
 
@@ -124,7 +128,7 @@ public void trackPlay(View view) {
                 90
         );
         // NOTE: For videos embedded in an article, "url" should be the URL for that article.
-        ParselyTracker.sharedInstance().trackPlay("http://example.com/app-videos", "", metadata, null);
+        ParselyTracker.sharedInstance().trackPlay("http://example.com/app-videos", "", metadata, null, getSiteId());
 
     }
 
@@ -135,4 +139,12 @@ public void trackPause(View view) {
     public void trackReset(View view) {
         ParselyTracker.sharedInstance().resetVideo();
     }
+
+    private SiteIdSource getSiteId() {
+        Editable fromEditText = ((EditText) findViewById(R.id.custom_site_id)).getText();
+        if (fromEditText == null || fromEditText.toString().isEmpty()) {
+            return SiteIdSource.Default.INSTANCE;
+        }
+        return new SiteIdSource.Custom(fromEditText.toString());
+    }
 }
diff --git a/example/src/main/res/layout/activity_main.xml b/example/src/main/res/layout/activity_main.xml
index e86a9223..bae2bae9 100644
--- a/example/src/main/res/layout/activity_main.xml
+++ b/example/src/main/res/layout/activity_main.xml
@@ -7,19 +7,27 @@
     android:paddingRight="@dimen/activity_horizontal_margin"
     android:paddingTop="@dimen/activity_vertical_margin"
     tools:context=".MainActivity" >
-    
+
     <ImageView
         android:id="@+id/imageView1"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_centerHorizontal="true"
         android:src="@drawable/parsely_logo_horizontal" />
-        
+
+    <EditText
+        android:id="@+id/custom_site_id"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_below="@id/imageView1"
+        android:layout_centerHorizontal="true"
+        android:hint="Custom site id. Default if empty"/>
+
     <Button android:id="@+id/url_button"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_centerHorizontal="true"
-        android:layout_below="@id/imageView1"
+        android:layout_below="@id/custom_site_id"
         android:text="@string/button_track_url"
         android:onClick="trackPageview" />
 
diff --git a/parsely/api/parsely.api b/parsely/api/parsely.api
index bc5179a6..b7b47f19 100644
--- a/parsely/api/parsely.api
+++ b/parsely/api/parsely.api
@@ -19,11 +19,11 @@ public abstract interface class com/parsely/parselyandroid/ParselyTracker {
 	public static fun init (Ljava/lang/String;Landroid/content/Context;)V
 	public abstract fun resetVideo ()V
 	public static fun sharedInstance ()Lcom/parsely/parselyandroid/ParselyTracker;
-	public abstract fun startEngagement (Ljava/lang/String;Ljava/lang/String;Ljava/util/Map;)V
+	public abstract fun startEngagement (Ljava/lang/String;Ljava/lang/String;Ljava/util/Map;Lcom/parsely/parselyandroid/SiteIdSource;)V
 	public abstract fun stopEngagement ()V
-	public abstract fun trackPageview (Ljava/lang/String;Ljava/lang/String;Lcom/parsely/parselyandroid/ParselyMetadata;Ljava/util/Map;)V
+	public abstract fun trackPageview (Ljava/lang/String;Ljava/lang/String;Lcom/parsely/parselyandroid/ParselyMetadata;Ljava/util/Map;Lcom/parsely/parselyandroid/SiteIdSource;)V
 	public abstract fun trackPause ()V
-	public abstract fun trackPlay (Ljava/lang/String;Ljava/lang/String;Lcom/parsely/parselyandroid/ParselyVideoMetadata;Ljava/util/Map;)V
+	public abstract fun trackPlay (Ljava/lang/String;Ljava/lang/String;Lcom/parsely/parselyandroid/ParselyVideoMetadata;Ljava/util/Map;Lcom/parsely/parselyandroid/SiteIdSource;)V
 }
 
 public final class com/parsely/parselyandroid/ParselyTracker$Companion {
@@ -35,9 +35,9 @@ public final class com/parsely/parselyandroid/ParselyTracker$Companion {
 }
 
 public final class com/parsely/parselyandroid/ParselyTracker$DefaultImpls {
-	public static synthetic fun startEngagement$default (Lcom/parsely/parselyandroid/ParselyTracker;Ljava/lang/String;Ljava/lang/String;Ljava/util/Map;ILjava/lang/Object;)V
-	public static synthetic fun trackPageview$default (Lcom/parsely/parselyandroid/ParselyTracker;Ljava/lang/String;Ljava/lang/String;Lcom/parsely/parselyandroid/ParselyMetadata;Ljava/util/Map;ILjava/lang/Object;)V
-	public static synthetic fun trackPlay$default (Lcom/parsely/parselyandroid/ParselyTracker;Ljava/lang/String;Ljava/lang/String;Lcom/parsely/parselyandroid/ParselyVideoMetadata;Ljava/util/Map;ILjava/lang/Object;)V
+	public static synthetic fun startEngagement$default (Lcom/parsely/parselyandroid/ParselyTracker;Ljava/lang/String;Ljava/lang/String;Ljava/util/Map;Lcom/parsely/parselyandroid/SiteIdSource;ILjava/lang/Object;)V
+	public static synthetic fun trackPageview$default (Lcom/parsely/parselyandroid/ParselyTracker;Ljava/lang/String;Ljava/lang/String;Lcom/parsely/parselyandroid/ParselyMetadata;Ljava/util/Map;Lcom/parsely/parselyandroid/SiteIdSource;ILjava/lang/Object;)V
+	public static synthetic fun trackPlay$default (Lcom/parsely/parselyandroid/ParselyTracker;Ljava/lang/String;Ljava/lang/String;Lcom/parsely/parselyandroid/ParselyVideoMetadata;Ljava/util/Map;Lcom/parsely/parselyandroid/SiteIdSource;ILjava/lang/Object;)V
 }
 
 public final class com/parsely/parselyandroid/ParselyVideoMetadata : com/parsely/parselyandroid/ParselyMetadata {
@@ -45,3 +45,24 @@ public final class com/parsely/parselyandroid/ParselyVideoMetadata : com/parsely
 	public synthetic fun <init> (Ljava/util/List;Ljava/lang/String;Ljava/lang/String;Ljava/util/List;Ljava/lang/String;Ljava/lang/String;Ljava/util/Calendar;IILkotlin/jvm/internal/DefaultConstructorMarker;)V
 }
 
+public abstract class com/parsely/parselyandroid/SiteIdSource {
+}
+
+public final class com/parsely/parselyandroid/SiteIdSource$Custom : com/parsely/parselyandroid/SiteIdSource {
+	public fun <init> (Ljava/lang/String;)V
+	public final fun component1 ()Ljava/lang/String;
+	public final fun copy (Ljava/lang/String;)Lcom/parsely/parselyandroid/SiteIdSource$Custom;
+	public static synthetic fun copy$default (Lcom/parsely/parselyandroid/SiteIdSource$Custom;Ljava/lang/String;ILjava/lang/Object;)Lcom/parsely/parselyandroid/SiteIdSource$Custom;
+	public fun equals (Ljava/lang/Object;)Z
+	public final fun getSiteId ()Ljava/lang/String;
+	public fun hashCode ()I
+	public fun toString ()Ljava/lang/String;
+}
+
+public final class com/parsely/parselyandroid/SiteIdSource$Default : com/parsely/parselyandroid/SiteIdSource {
+	public static final field INSTANCE Lcom/parsely/parselyandroid/SiteIdSource$Default;
+	public fun equals (Ljava/lang/Object;)Z
+	public fun hashCode ()I
+	public fun toString ()Ljava/lang/String;
+}
+
diff --git a/parsely/src/androidTest/java/com/parsely/parselyandroid/FunctionalTests.kt b/parsely/src/androidTest/java/com/parsely/parselyandroid/FunctionalTests.kt
index 4d555df3..9dfa2225 100644
--- a/parsely/src/androidTest/java/com/parsely/parselyandroid/FunctionalTests.kt
+++ b/parsely/src/androidTest/java/com/parsely/parselyandroid/FunctionalTests.kt
@@ -282,6 +282,46 @@ class FunctionalTests {
         }
     }
 
+    /**
+     * In this scenario, the consumer app starts an engagement session and configures siteId
+     * with a custom value for the session.
+     *
+     * Intervals:
+     * With current implementation of `HeartbeatIntervalCalculator`, the next intervals are:
+     * - 10500ms for the first interval
+     * - 13650ms for the second interval
+     *
+     * So after ~27,2s we should observe 2 `heartbeat` events from `startEngagement`.
+     *
+     * They both should have the same custom site id.
+     */
+    @Test
+    fun customSiteIdIsAppliedToConcurrentEventsInEngagementSession() {
+        ActivityScenario.launch(SampleActivity::class.java).use { scenario ->
+            // given
+            val customSiteId = "customSiteId"
+            val flushInterval = 30.seconds
+            scenario.onActivity { activity: Activity ->
+                beforeEach(activity)
+                server.enqueue(MockResponse().setResponseCode(200))
+                initializeTracker(activity, flushInterval)
+
+                // when
+                parselyTracker.trackPageview("engagementUrl")
+                parselyTracker.startEngagement("engagementUrl", siteIdSource = SiteIdSource.Custom(customSiteId))
+            }
+
+            // then
+            val request = server.takeRequest().toMap()["events"]!!
+
+            assertThat(request.filter { it.action=="heartbeat" }).hasSize(2)
+                .allSatisfy {
+                    assertThat(it.idsite).isEqualTo(customSiteId)
+                }
+        }
+
+    }
+
     private fun RecordedRequest.toMap(): Map<String, List<Event>> {
         val listType: TypeReference<Map<String, List<Event>>> =
             object : TypeReference<Map<String, List<Event>>>() {}
diff --git a/parsely/src/main/java/com/parsely/parselyandroid/ConnectivityStatusProvider.kt b/parsely/src/main/java/com/parsely/parselyandroid/ConnectivityStatusProvider.kt
index f7d90842..4ef76e24 100644
--- a/parsely/src/main/java/com/parsely/parselyandroid/ConnectivityStatusProvider.kt
+++ b/parsely/src/main/java/com/parsely/parselyandroid/ConnectivityStatusProvider.kt
@@ -10,7 +10,8 @@ internal interface ConnectivityStatusProvider {
     fun isReachable(): Boolean
 }
 
-internal class AndroidConnectivityStatusProvider(private val context: Context): ConnectivityStatusProvider {
+internal class AndroidConnectivityStatusProvider(private val context: Context):
+    ConnectivityStatusProvider {
 
     override fun isReachable(): Boolean {
         val cm = context.getSystemService(
diff --git a/parsely/src/main/java/com/parsely/parselyandroid/EventsBuilder.kt b/parsely/src/main/java/com/parsely/parselyandroid/EventsBuilder.kt
index 945c8b33..e3783056 100644
--- a/parsely/src/main/java/com/parsely/parselyandroid/EventsBuilder.kt
+++ b/parsely/src/main/java/com/parsely/parselyandroid/EventsBuilder.kt
@@ -1,12 +1,10 @@
 package com.parsely.parselyandroid
 
 import com.parsely.parselyandroid.Logging.log
-import java.util.Calendar
-import java.util.TimeZone
 
 internal class EventsBuilder(
     private val deviceInfoRepository: DeviceInfoRepository,
-    private val siteId: String,
+    private val initializationSiteId: String,
     private val clock: Clock,
 ) {
     /**
@@ -16,6 +14,8 @@ internal class EventsBuilder(
      * @param action    Action to use (e.g. pageview, heartbeat, videostart, vheartbeat)
      * @param metadata  Metadata to attach to the event.
      * @param extraData A Map of additional information to send with the event.
+     * @param uuid      A unique identifier for the event.
+     * @param siteIdSource The source of the site ID to use for the event.
      * @return A Map object representing the event to be sent to Parse.ly.
      */
     fun buildEvent(
@@ -24,7 +24,8 @@ internal class EventsBuilder(
         action: String,
         metadata: ParselyMetadata?,
         extraData: Map<String, Any>?,
-        uuid: String
+        uuid: String,
+        siteIdSource: SiteIdSource,
     ): Map<String, Any> {
         log("buildEvent called for %s/%s", action, url)
 
@@ -32,7 +33,10 @@ internal class EventsBuilder(
         val event: MutableMap<String, Any> = HashMap()
         event["url"] = url
         event["urlref"] = urlRef
-        event["idsite"] = siteId
+        event["idsite"] = when (siteIdSource) {
+            is SiteIdSource.Default -> initializationSiteId
+            is SiteIdSource.Custom -> siteIdSource.siteId
+        }
         event["action"] = action
 
         // Make a copy of extraData and add some things.
diff --git a/parsely/src/main/java/com/parsely/parselyandroid/FlushQueue.kt b/parsely/src/main/java/com/parsely/parselyandroid/FlushQueue.kt
index b5779d5f..561e7c19 100644
--- a/parsely/src/main/java/com/parsely/parselyandroid/FlushQueue.kt
+++ b/parsely/src/main/java/com/parsely/parselyandroid/FlushQueue.kt
@@ -31,13 +31,13 @@ internal class FlushQueue(
                     return@launch
                 }
 
+                val jsonPayload = toParselyEventsPayload(eventsToSend)
                 if (skipSendingEvents) {
-                    log("Debug mode on. Not sending to Parse.ly. Otherwise, would sent ${eventsToSend.size} events")
+                    log("Debug mode on. Not sending to Parse.ly. Otherwise, would sent ${eventsToSend.size} events: $jsonPayload")
                     repository.remove(eventsToSend)
                     return@launch
                 }
                 log("Sending request with %d events", eventsToSend.size)
-                val jsonPayload = toParselyEventsPayload(eventsToSend)
                 log("POST Data %s", jsonPayload)
                 log("Requested %s", ParselyTrackerInternal.ROOT_URL)
                 restClient.send(jsonPayload)
diff --git a/parsely/src/main/java/com/parsely/parselyandroid/ParselyTracker.kt b/parsely/src/main/java/com/parsely/parselyandroid/ParselyTracker.kt
index 3ee7a63a..b8155bcc 100644
--- a/parsely/src/main/java/com/parsely/parselyandroid/ParselyTracker.kt
+++ b/parsely/src/main/java/com/parsely/parselyandroid/ParselyTracker.kt
@@ -36,12 +36,16 @@ public interface ParselyTracker {
      *                    content). Do not use this for **content also hosted on** URLs Parse.ly
      *                    would normally crawl.
      * @param extraData   A Map of additional information to send with the event.
+     * @param siteIdSource The source of the site ID to use for the event. If [SiteIdSource.Default],
+     *                     the site ID provided during [init] will be used. Otherwise, the site ID
+     *                     provided in the [SiteIdSource.Custom] object will be used.
      */
     public fun trackPageview(
         url: String,
         urlRef: String = "",
         urlMetadata: ParselyMetadata? = null,
         extraData: Map<String, Any>? = null,
+        siteIdSource: SiteIdSource = SiteIdSource.Default,
     )
 
     /**
@@ -59,11 +63,13 @@ public interface ParselyTracker {
      * @param url    The URL of the tracked article (eg: “http://example.com/some-old/article.html“)
      * @param urlRef The url of the page that linked to the page being engaged with. Analogous to HTTP referer
      * @param extraData A map of additional information to send with the generated `heartbeat` events
+     * @param siteIdSource The source of the site ID to use for the event.
      */
     public fun startEngagement(
         url: String,
         urlRef: String = "",
-        extraData: Map<String, Any>? = null
+        extraData: Map<String, Any>? = null,
+        siteIdSource: SiteIdSource = SiteIdSource.Default,
     )
 
     /**
@@ -96,12 +102,14 @@ public interface ParselyTracker {
      * @param urlRef        The url of the page that linked to the page being engaged with. Analogous to HTTP referer
      * @param videoMetadata Metadata about the tracked video
      * @param extraData     A Map of additional information to send with the event
+     * @param siteIdSource The source of the site ID to use for the event.
      */
     public fun trackPlay(
         url: String,
         urlRef: String = "",
         videoMetadata: ParselyVideoMetadata,
         extraData: Map<String, Any>? = null,
+        siteIdSource: SiteIdSource = SiteIdSource.Default,
     )
 
     /**
diff --git a/parsely/src/main/java/com/parsely/parselyandroid/ParselyTrackerInternal.kt b/parsely/src/main/java/com/parsely/parselyandroid/ParselyTrackerInternal.kt
index a88a999c..66333c86 100644
--- a/parsely/src/main/java/com/parsely/parselyandroid/ParselyTrackerInternal.kt
+++ b/parsely/src/main/java/com/parsely/parselyandroid/ParselyTrackerInternal.kt
@@ -89,6 +89,7 @@ internal class ParselyTrackerInternal internal constructor(
         urlRef: String,
         urlMetadata: ParselyMetadata?,
         extraData: Map<String, Any>?,
+        siteIdSource: SiteIdSource,
     ) {
         if (url.isBlank()) {
             Logging.log("url cannot be empty")
@@ -105,7 +106,8 @@ internal class ParselyTrackerInternal internal constructor(
                 "pageview",
                 urlMetadata,
                 extraData,
-                pageViewUuid
+                pageViewUuid,
+                siteIdSource
             )
         )
     }
@@ -113,7 +115,8 @@ internal class ParselyTrackerInternal internal constructor(
     override fun startEngagement(
         url: String,
         urlRef: String,
-        extraData: Map<String, Any>?
+        extraData: Map<String, Any>?,
+        siteIdSource: SiteIdSource,
     ) {
         if (url.isBlank()) {
             Logging.log("url cannot be empty")
@@ -130,7 +133,7 @@ internal class ParselyTrackerInternal internal constructor(
 
         // Start a new EngagementTask
         val event =
-            eventsBuilder.buildEvent(url, urlRef, "heartbeat", null, extraData, pageViewUuid)
+            eventsBuilder.buildEvent(url, urlRef, "heartbeat", null, extraData, pageViewUuid, siteIdSource)
         engagementManager = EngagementManager(
             this,
             DEFAULT_ENGAGEMENT_INTERVAL_MILLIS.toLong(),
@@ -154,6 +157,7 @@ internal class ParselyTrackerInternal internal constructor(
         urlRef: String,
         videoMetadata: ParselyVideoMetadata,
         extraData: Map<String, Any>?,
+        siteIdSource: SiteIdSource,
     ) {
         if (url.isBlank()) {
             Logging.log("url cannot be empty")
@@ -176,12 +180,12 @@ internal class ParselyTrackerInternal internal constructor(
 
         // Enqueue the videostart
         val videostartEvent =
-            eventsBuilder.buildEvent(url, urlRef, "videostart", videoMetadata, extraData, uuid)
+            eventsBuilder.buildEvent(url, urlRef, "videostart", videoMetadata, extraData, uuid, siteIdSource)
         enqueueEvent(videostartEvent)
 
         // Start a new engagement manager for the video.
         val hbEvent =
-            eventsBuilder.buildEvent(url, urlRef, "vheartbeat", videoMetadata, extraData, uuid)
+            eventsBuilder.buildEvent(url, urlRef, "vheartbeat", videoMetadata, extraData, uuid, siteIdSource)
         // TODO: Can we remove some metadata fields from this request?
         videoEngagementManager = EngagementManager(
             this,
diff --git a/parsely/src/main/java/com/parsely/parselyandroid/SiteIdSource.kt b/parsely/src/main/java/com/parsely/parselyandroid/SiteIdSource.kt
new file mode 100644
index 00000000..b72f90e2
--- /dev/null
+++ b/parsely/src/main/java/com/parsely/parselyandroid/SiteIdSource.kt
@@ -0,0 +1,18 @@
+package com.parsely.parselyandroid
+
+/**
+ * Configuration for the site ID to be used for an event.
+ */
+public sealed class SiteIdSource {
+    /**
+     * Instruct SDK to use site ID provided during [ParselyTracker.init].
+     */
+    public data object Default : SiteIdSource()
+
+    /**
+     * Instruct SDK to override the site ID for the event.
+     *
+     * @param siteId The Parsely public site ID (e.g. "example.com") to use for the event.
+     */
+    public data class Custom(val siteId: String) : SiteIdSource()
+}
diff --git a/parsely/src/test/java/com/parsely/parselyandroid/EngagementManagerTest.kt b/parsely/src/test/java/com/parsely/parselyandroid/EngagementManagerTest.kt
index 45b797c5..0848b3c6 100644
--- a/parsely/src/test/java/com/parsely/parselyandroid/EngagementManagerTest.kt
+++ b/parsely/src/test/java/com/parsely/parselyandroid/EngagementManagerTest.kt
@@ -1,6 +1,5 @@
 package com.parsely.parselyandroid
 
-import androidx.test.core.app.ApplicationProvider
 import kotlin.time.Duration
 import kotlin.time.Duration.Companion.milliseconds
 import kotlin.time.Duration.Companion.seconds
diff --git a/parsely/src/test/java/com/parsely/parselyandroid/EventsBuilderTest.kt b/parsely/src/test/java/com/parsely/parselyandroid/EventsBuilderTest.kt
index 05af5efb..cec50c7c 100644
--- a/parsely/src/test/java/com/parsely/parselyandroid/EventsBuilderTest.kt
+++ b/parsely/src/test/java/com/parsely/parselyandroid/EventsBuilderTest.kt
@@ -30,6 +30,7 @@ internal class EventsBuilderTest {
             null,
             null,
             TEST_UUID,
+            SiteIdSource.Default,
         )
 
         // then
@@ -49,6 +50,7 @@ internal class EventsBuilderTest {
             null,
             null,
             TEST_UUID,
+            SiteIdSource.Default,
         )
 
         // then
@@ -68,6 +70,7 @@ internal class EventsBuilderTest {
             null,
             null,
             TEST_UUID,
+            SiteIdSource.Default,
         )
 
         // then
@@ -87,6 +90,7 @@ internal class EventsBuilderTest {
             null,
             null,
             TEST_UUID,
+            SiteIdSource.Default,
         )
 
         // then
@@ -109,6 +113,7 @@ internal class EventsBuilderTest {
             null,
             extraData,
             TEST_UUID,
+            SiteIdSource.Default,
         )
 
         // then
@@ -132,6 +137,7 @@ internal class EventsBuilderTest {
             null,
             extraData,
             TEST_UUID,
+            SiteIdSource.Default,
         )
 
         // then
@@ -153,6 +159,7 @@ internal class EventsBuilderTest {
             metadata,
             null,
             TEST_UUID,
+            SiteIdSource.Default,
         )
 
         // then
@@ -174,12 +181,51 @@ internal class EventsBuilderTest {
             metadata,
             null,
             TEST_UUID,
+            SiteIdSource.Default,
         )
 
         // then
         assertThat(event).containsKey("metadata")
     }
 
+    @Test
+    fun `given default site id is provided, when creating a pixel, then use the default site id`() {
+        // when
+        val event: Map<String, Any> = sut.buildEvent(
+            TEST_URL,
+            "",
+            "pageview",
+            null,
+            null,
+            TEST_UUID,
+            SiteIdSource.Default,
+        )
+
+        // then
+        assertThat(event).containsEntry("idsite", TEST_SITE_ID)
+    }
+
+
+    @Test
+    fun `given custom site id is provided, when creating a pixel, then use the custom site id`() {
+        // given
+        val customSiteId = "Custom Site ID"
+
+        // when
+        val event: Map<String, Any> = sut.buildEvent(
+            TEST_URL,
+            "",
+            "pageview",
+            null,
+            null,
+            TEST_UUID,
+            SiteIdSource.Custom(customSiteId),
+        )
+
+        // then
+        assertThat(event).containsEntry("idsite", customSiteId)
+    }
+
     private fun MapAssert<String, Any>.sharedPixelAssertions() =
         hasSize(6)
             .containsEntry("url", TEST_URL)
diff --git a/parsely/src/test/java/com/parsely/parselyandroid/HeartbeatIntervalCalculatorTest.kt b/parsely/src/test/java/com/parsely/parselyandroid/HeartbeatIntervalCalculatorTest.kt
index eb5c420e..62e90040 100644
--- a/parsely/src/test/java/com/parsely/parselyandroid/HeartbeatIntervalCalculatorTest.kt
+++ b/parsely/src/test/java/com/parsely/parselyandroid/HeartbeatIntervalCalculatorTest.kt
@@ -1,7 +1,6 @@
 package com.parsely.parselyandroid
 
 import com.parsely.parselyandroid.HeartbeatIntervalCalculator.Companion.MAX_TIME_BETWEEN_HEARTBEATS
-import java.util.Calendar
 import kotlin.time.Duration
 import kotlin.time.Duration.Companion.seconds
 import org.assertj.core.api.Assertions.assertThat