diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 3489c34bbc..8415f57c9a 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -40,6 +40,7 @@
   ([#5619](https://github.com/google/ExoPlayer/issues/5619)).
 * Fix issue where player errors are thrown too early at playlist transitions
   ([#5407](https://github.com/google/ExoPlayer/issues/5407)).
+* Deprecate `setTag` parameter of `Timeline.getWindow`. Tags will always be set.
 
 ### 2.10.4 ###
 
diff --git a/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastTimeline.java b/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastTimeline.java
index b84f1c1f2b..58dbec611a 100644
--- a/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastTimeline.java
+++ b/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/CastTimeline.java
@@ -110,13 +110,11 @@ import java.util.Arrays;
   }
 
   @Override
-  public Window getWindow(
-      int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
+  public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
     long durationUs = durationsUs[windowIndex];
     boolean isDynamic = durationUs == C.TIME_UNSET;
-    Object tag = setTag ? ids[windowIndex] : null;
     return window.set(
-        tag,
+        /* tag= */ ids[windowIndex],
         /* manifest= */ null,
         /* presentationStartTimeMs= */ C.TIME_UNSET,
         /* windowStartTimeMs= */ C.TIME_UNSET,
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/BasePlayer.java b/library/core/src/main/java/com/google/android/exoplayer2/BasePlayer.java
index bb14ac147b..1b3e57cede 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/BasePlayer.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/BasePlayer.java
@@ -95,18 +95,14 @@ public abstract class BasePlayer implements Player {
   @Nullable
   public final Object getCurrentTag() {
     Timeline timeline = getCurrentTimeline();
-    return timeline.isEmpty()
-        ? null
-        : timeline.getWindow(getCurrentWindowIndex(), window, /* setTag= */ true).tag;
+    return timeline.isEmpty() ? null : timeline.getWindow(getCurrentWindowIndex(), window).tag;
   }
 
   @Override
   @Nullable
   public final Object getCurrentManifest() {
     Timeline timeline = getCurrentTimeline();
-    return timeline.isEmpty()
-        ? null
-        : timeline.getWindow(getCurrentWindowIndex(), window, /* setTag= */ false).manifest;
+    return timeline.isEmpty() ? null : timeline.getWindow(getCurrentWindowIndex(), window).manifest;
   }
 
   @Override
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/Timeline.java b/library/core/src/main/java/com/google/android/exoplayer2/Timeline.java
index 8d5731da20..57d3d8bf1d 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/Timeline.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/Timeline.java
@@ -520,8 +520,7 @@ public abstract class Timeline {
         }
 
         @Override
-        public Window getWindow(
-            int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
+        public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
           throw new IndexOutOfBoundsException();
         }
 
@@ -633,28 +632,20 @@ public abstract class Timeline {
   }
 
   /**
-   * Populates a {@link Window} with data for the window at the specified index. Does not populate
-   * {@link Window#tag}.
+   * Populates a {@link Window} with data for the window at the specified index.
    *
    * @param windowIndex The index of the window.
    * @param window The {@link Window} to populate. Must not be null.
    * @return The populated {@link Window}, for convenience.
    */
   public final Window getWindow(int windowIndex, Window window) {
-    return getWindow(windowIndex, window, false);
+    return getWindow(windowIndex, window, /* defaultPositionProjectionUs= */ 0);
   }
 
-  /**
-   * Populates a {@link Window} with data for the window at the specified index.
-   *
-   * @param windowIndex The index of the window.
-   * @param window The {@link Window} to populate. Must not be null.
-   * @param setTag Whether {@link Window#tag} should be populated. If false, the field will be set
-   *     to null. The caller should pass false for efficiency reasons unless the field is required.
-   * @return The populated {@link Window}, for convenience.
-   */
+  /** @deprecated Use {@link #getWindow(int, Window)} instead. Tags will always be set. */
+  @Deprecated
   public final Window getWindow(int windowIndex, Window window, boolean setTag) {
-    return getWindow(windowIndex, window, setTag, 0);
+    return getWindow(windowIndex, window, /* defaultPositionProjectionUs= */ 0);
   }
 
   /**
@@ -662,14 +653,21 @@ public abstract class Timeline {
    *
    * @param windowIndex The index of the window.
    * @param window The {@link Window} to populate. Must not be null.
-   * @param setTag Whether {@link Window#tag} should be populated. If false, the field will be set
-   *     to null. The caller should pass false for efficiency reasons unless the field is required.
    * @param defaultPositionProjectionUs A duration into the future that the populated window's
    *     default start position should be projected.
    * @return The populated {@link Window}, for convenience.
    */
-  public abstract Window getWindow(
-      int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs);
+  @SuppressWarnings("deprecation")
+  public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
+    return getWindow(windowIndex, window, /* setTag= */ true, defaultPositionProjectionUs);
+  }
+
+  /** @deprecated Implement {@link #getWindow(int, Window, long)} instead and always set the tag. */
+  @Deprecated
+  public Window getWindow(
+      int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
+    return getWindow(windowIndex, window, defaultPositionProjectionUs);
+  }
 
   /**
    * Returns the number of periods in the timeline.
@@ -750,7 +748,7 @@ public abstract class Timeline {
       long windowPositionUs,
       long defaultPositionProjectionUs) {
     Assertions.checkIndex(windowIndex, 0, getWindowCount());
-    getWindow(windowIndex, window, false, defaultPositionProjectionUs);
+    getWindow(windowIndex, window, defaultPositionProjectionUs);
     if (windowPositionUs == C.TIME_UNSET) {
       windowPositionUs = window.getDefaultPositionUs();
       if (windowPositionUs == C.TIME_UNSET) {
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/AbstractConcatenatedTimeline.java b/library/core/src/main/java/com/google/android/exoplayer2/source/AbstractConcatenatedTimeline.java
index db19764318..4e7b572384 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/AbstractConcatenatedTimeline.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/AbstractConcatenatedTimeline.java
@@ -189,14 +189,12 @@ import com.google.android.exoplayer2.util.Assertions;
   }
 
   @Override
-  public final Window getWindow(
-      int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
+  public final Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
     int childIndex = getChildIndexByWindowIndex(windowIndex);
     int firstWindowIndexInChild = getFirstWindowIndexByChildIndex(childIndex);
     int firstPeriodIndexInChild = getFirstPeriodIndexByChildIndex(childIndex);
     getTimelineByChildIndex(childIndex)
-        .getWindow(
-            windowIndex - firstWindowIndexInChild, window, setTag, defaultPositionProjectionUs);
+        .getWindow(windowIndex - firstWindowIndexInChild, window, defaultPositionProjectionUs);
     window.firstPeriodIndex += firstPeriodIndexInChild;
     window.lastPeriodIndex += firstPeriodIndexInChild;
     return window;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java
index 81169354de..703f8bafc0 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ClippingMediaSource.java
@@ -342,10 +342,8 @@ public final class ClippingMediaSource extends CompositeMediaSource<Void> {
     }
 
     @Override
-    public Window getWindow(
-        int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
-      timeline.getWindow(
-          /* windowIndex= */ 0, window, setTag, /* defaultPositionProjectionUs= */ 0);
+    public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
+      timeline.getWindow(/* windowIndex= */ 0, window, /* defaultPositionProjectionUs= */ 0);
       window.positionInFirstPeriodUs += startUs;
       window.durationUs = durationUs;
       window.isDynamic = isDynamic;
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ForwardingTimeline.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ForwardingTimeline.java
index 45997aced4..38b373b26c 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ForwardingTimeline.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ForwardingTimeline.java
@@ -57,9 +57,8 @@ public abstract class ForwardingTimeline extends Timeline {
   }
 
   @Override
-  public Window getWindow(
-      int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
-    return timeline.getWindow(windowIndex, window, setTag, defaultPositionProjectionUs);
+  public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
+    return timeline.getWindow(windowIndex, window, defaultPositionProjectionUs);
   }
 
   @Override
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/MaskingMediaSource.java b/library/core/src/main/java/com/google/android/exoplayer2/source/MaskingMediaSource.java
index d9dd83de4f..35800f56da 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/MaskingMediaSource.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/MaskingMediaSource.java
@@ -287,8 +287,7 @@ public final class MaskingMediaSource extends CompositeMediaSource<Void> {
     }
 
     @Override
-    public Window getWindow(
-        int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
+    public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
       return window.set(
           tag,
           /* manifest= */ null,
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java b/library/core/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java
index 8790b09f07..966f8e4c7a 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/SinglePeriodTimeline.java
@@ -159,10 +159,8 @@ public final class SinglePeriodTimeline extends Timeline {
   }
 
   @Override
-  public Window getWindow(
-      int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
+  public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
     Assertions.checkIndex(windowIndex, 0, 1);
-    Object tag = setTag ? this.tag : null;
     long windowDefaultStartPositionUs = this.windowDefaultStartPositionUs;
     if (isDynamic && defaultPositionProjectionUs != 0) {
       if (windowDurationUs == C.TIME_UNSET) {
diff --git a/library/core/src/main/java/com/google/android/exoplayer2/source/ads/SinglePeriodAdTimeline.java b/library/core/src/main/java/com/google/android/exoplayer2/source/ads/SinglePeriodAdTimeline.java
index 25a1440c80..b5167dc173 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/source/ads/SinglePeriodAdTimeline.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/source/ads/SinglePeriodAdTimeline.java
@@ -55,9 +55,8 @@ public final class SinglePeriodAdTimeline extends ForwardingTimeline {
   }
 
   @Override
-  public Window getWindow(
-      int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
-    window = super.getWindow(windowIndex, window, setTag, defaultPositionProjectionUs);
+  public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
+    window = super.getWindow(windowIndex, window, defaultPositionProjectionUs);
     if (window.durationUs == C.TIME_UNSET) {
       window.durationUs = adPlaybackState.contentDurationUs;
     }
diff --git a/library/core/src/test/java/com/google/android/exoplayer2/source/SinglePeriodTimelineTest.java b/library/core/src/test/java/com/google/android/exoplayer2/source/SinglePeriodTimelineTest.java
index 701ec3521c..cb21db8212 100644
--- a/library/core/src/test/java/com/google/android/exoplayer2/source/SinglePeriodTimelineTest.java
+++ b/library/core/src/test/java/com/google/android/exoplayer2/source/SinglePeriodTimelineTest.java
@@ -88,8 +88,7 @@ public final class SinglePeriodTimelineTest {
             /* manifest= */ null,
             /* tag= */ null);
 
-    assertThat(timeline.getWindow(/* windowIndex= */ 0, window, /* setTag= */ false).tag).isNull();
-    assertThat(timeline.getWindow(/* windowIndex= */ 0, window, /* setTag= */ true).tag).isNull();
+    assertThat(timeline.getWindow(/* windowIndex= */ 0, window).tag).isNull();
     assertThat(timeline.getPeriod(/* periodIndex= */ 0, period, /* setIds= */ false).id).isNull();
     assertThat(timeline.getPeriod(/* periodIndex= */ 0, period, /* setIds= */ true).id).isNull();
     assertThat(timeline.getPeriod(/* periodIndex= */ 0, period, /* setIds= */ false).uid).isNull();
@@ -98,7 +97,7 @@ public final class SinglePeriodTimelineTest {
   }
 
   @Test
-  public void setTag_isUsedForWindowTag() {
+  public void getWindow_setsTag() {
     Object tag = new Object();
     SinglePeriodTimeline timeline =
         new SinglePeriodTimeline(
@@ -108,9 +107,7 @@ public final class SinglePeriodTimelineTest {
             /* manifest= */ null,
             tag);
 
-    assertThat(timeline.getWindow(/* windowIndex= */ 0, window, /* setTag= */ false).tag).isNull();
-    assertThat(timeline.getWindow(/* windowIndex= */ 0, window, /* setTag= */ true).tag)
-        .isEqualTo(tag);
+    assertThat(timeline.getWindow(/* windowIndex= */ 0, window).tag).isEqualTo(tag);
   }
 
   @Test
diff --git a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
index 890a272c5e..1b163c02e2 100644
--- a/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
+++ b/library/dash/src/main/java/com/google/android/exoplayer2/source/dash/DashMediaSource.java
@@ -1207,18 +1207,16 @@ public final class DashMediaSource extends BaseMediaSource {
     }
 
     @Override
-    public Window getWindow(
-        int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
+    public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
       Assertions.checkIndex(windowIndex, 0, 1);
       long windowDefaultStartPositionUs = getAdjustedWindowDefaultStartPositionUs(
           defaultPositionProjectionUs);
-      Object tag = setTag ? windowTag : null;
       boolean isDynamic =
           manifest.dynamic
               && manifest.minUpdatePeriodMs != C.TIME_UNSET
               && manifest.durationMs == C.TIME_UNSET;
       return window.set(
-          tag,
+          windowTag,
           manifest,
           presentationStartTimeMs,
           windowStartTimeMs,
diff --git a/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeTimeline.java b/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeTimeline.java
index 58ee32cdd9..f0a0c77ff6 100644
--- a/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeTimeline.java
+++ b/testutils/src/main/java/com/google/android/exoplayer2/testutil/FakeTimeline.java
@@ -179,12 +179,10 @@ public final class FakeTimeline extends Timeline {
   }
 
   @Override
-  public Window getWindow(
-      int windowIndex, Window window, boolean setTag, long defaultPositionProjectionUs) {
+  public Window getWindow(int windowIndex, Window window, long defaultPositionProjectionUs) {
     TimelineWindowDefinition windowDefinition = windowDefinitions[windowIndex];
-    Object tag = setTag ? windowDefinition.id : null;
     return window.set(
-        tag,
+        /* tag= */ windowDefinition.id,
         manifests[windowIndex],
         /* presentationStartTimeMs= */ C.TIME_UNSET,
         /* windowStartTimeMs= */ C.TIME_UNSET,
diff --git a/testutils/src/main/java/com/google/android/exoplayer2/testutil/TimelineAsserts.java b/testutils/src/main/java/com/google/android/exoplayer2/testutil/TimelineAsserts.java
index 1e3c9c61d9..f3ec47a88b 100644
--- a/testutils/src/main/java/com/google/android/exoplayer2/testutil/TimelineAsserts.java
+++ b/testutils/src/main/java/com/google/android/exoplayer2/testutil/TimelineAsserts.java
@@ -52,7 +52,7 @@ public final class TimelineAsserts {
     Window window = new Window();
     assertThat(timeline.getWindowCount()).isEqualTo(expectedWindowTags.length);
     for (int i = 0; i < timeline.getWindowCount(); i++) {
-      timeline.getWindow(i, window, true);
+      timeline.getWindow(i, window);
       if (expectedWindowTags[i] != null) {
         assertThat(window.tag).isEqualTo(expectedWindowTags[i]);
       }
@@ -63,7 +63,7 @@ public final class TimelineAsserts {
   public static void assertWindowIsDynamic(Timeline timeline, boolean... windowIsDynamic) {
     Window window = new Window();
     for (int i = 0; i < timeline.getWindowCount(); i++) {
-      timeline.getWindow(i, window, true);
+      timeline.getWindow(i, window);
       assertThat(window.isDynamic).isEqualTo(windowIsDynamic[i]);
     }
   }
@@ -129,7 +129,7 @@ public final class TimelineAsserts {
     Window window = new Window();
     Period period = new Period();
     for (int i = 0; i < windowCount; i++) {
-      timeline.getWindow(i, window, true);
+      timeline.getWindow(i, window);
       assertThat(window.firstPeriodIndex).isEqualTo(accumulatedPeriodCounts[i]);
       assertThat(window.lastPeriodIndex).isEqualTo(accumulatedPeriodCounts[i + 1] - 1);
     }