diff --git a/libraries/transformer/build.gradle b/libraries/transformer/build.gradle
index 510f8eca97..00dfc401ab 100644
--- a/libraries/transformer/build.gradle
+++ b/libraries/transformer/build.gradle
@@ -15,6 +15,7 @@ apply from: "$gradle.ext.androidxMediaSettingsDir/common_library_config.gradle"
 android {
 
     defaultConfig {
+        minSdkVersion 21
         // The following argument makes the Android Test Orchestrator run its
         // "pm clear" command after each test invocation. This command ensures
         // that the app's state is completely cleared between tests.
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/AudioSamplePipeline.java b/libraries/transformer/src/main/java/androidx/media3/transformer/AudioSamplePipeline.java
index 76f7d51955..c98a858dae 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/AudioSamplePipeline.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/AudioSamplePipeline.java
@@ -23,7 +23,6 @@ import static java.lang.Math.min;
 
 import android.media.MediaCodec.BufferInfo;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
 import androidx.media3.common.PlaybackException;
@@ -41,7 +40,6 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 /**
  * Pipeline to decode audio samples, apply transformations on the raw samples, and re-encode them.
  */
-@RequiresApi(18)
 /* package */ final class AudioSamplePipeline implements SamplePipeline {
 
   private static final String TAG = "AudioSamplePipeline";
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/FrameEditor.java b/libraries/transformer/src/main/java/androidx/media3/transformer/FrameEditor.java
index dfad38037c..dc552d26f1 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/FrameEditor.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/FrameEditor.java
@@ -24,7 +24,6 @@ import android.opengl.EGLExt;
 import android.opengl.EGLSurface;
 import android.opengl.GLES20;
 import android.view.Surface;
-import androidx.annotation.RequiresApi;
 import androidx.media3.common.util.GlUtil;
 import java.io.IOException;
 
@@ -32,7 +31,6 @@ import java.io.IOException;
  * FrameEditor applies changes to individual video frames. Changes include just resolution for now,
  * but may later include brightness, cropping, rotation, etc.
  */
-@RequiresApi(18)
 /* package */ final class FrameEditor {
 
   static {
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/FrameworkMuxer.java b/libraries/transformer/src/main/java/androidx/media3/transformer/FrameworkMuxer.java
index e0d3456ba8..4ebe62e846 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/FrameworkMuxer.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/FrameworkMuxer.java
@@ -36,7 +36,6 @@ import java.lang.reflect.Field;
 import java.nio.ByteBuffer;
 
 /** Muxer implementation that uses a {@link MediaMuxer}. */
-@RequiresApi(18)
 /* package */ final class FrameworkMuxer implements Muxer {
 
   public static final class Factory implements Muxer.Factory {
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/MediaCodecAdapterWrapper.java b/libraries/transformer/src/main/java/androidx/media3/transformer/MediaCodecAdapterWrapper.java
index 8db4105660..e41174a4ee 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/MediaCodecAdapterWrapper.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/MediaCodecAdapterWrapper.java
@@ -26,7 +26,6 @@ import android.media.MediaCodecInfo.CodecCapabilities;
 import android.media.MediaFormat;
 import android.view.Surface;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
 import androidx.media3.common.MimeTypes;
@@ -50,7 +49,6 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
  * through {@link MediaCodecAdapter}. This is done by simplifying the calls needed to queue and
  * dequeue buffers, removing the need to track buffer indices and codec events.
  */
-@RequiresApi(18)
 /* package */ final class MediaCodecAdapterWrapper {
 
   // MediaCodec decoders always output 16 bit PCM, unless configured to output PCM float.
@@ -303,7 +301,6 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
     inputBuffer.data = null;
   }
 
-  @RequiresApi(18)
   public void signalEndOfInputStream() {
     codec.signalEndOfInputStream();
   }
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/MuxerWrapper.java b/libraries/transformer/src/main/java/androidx/media3/transformer/MuxerWrapper.java
index 83c18bd017..0bba625b21 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/MuxerWrapper.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/MuxerWrapper.java
@@ -22,7 +22,6 @@ import static androidx.media3.common.util.Util.minValue;
 import android.util.SparseIntArray;
 import android.util.SparseLongArray;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
 import androidx.media3.common.MimeTypes;
@@ -34,7 +33,6 @@ import java.nio.ByteBuffer;
  *
  * <p>This wrapper can contain at most one video track and one audio track.
  */
-@RequiresApi(18)
 /* package */ final class MuxerWrapper {
 
   /**
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/Transformer.java b/libraries/transformer/src/main/java/androidx/media3/transformer/Transformer.java
index c2f94abbf0..a51b93b64e 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/Transformer.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/Transformer.java
@@ -80,7 +80,6 @@ import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
  * of the application's main thread is used. In all cases the Looper of the thread from which the
  * transformer must be accessed can be queried using {@link #getApplicationLooper()}.
  */
-@RequiresApi(18)
 @UnstableApi
 public final class Transformer {
 
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerAudioRenderer.java b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerAudioRenderer.java
index 602cceb12c..f534bcfdca 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerAudioRenderer.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerAudioRenderer.java
@@ -20,7 +20,6 @@ import static androidx.media3.common.util.Assertions.checkNotNull;
 import static androidx.media3.exoplayer.source.SampleStream.FLAG_REQUIRE_FORMAT;
 
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
 import androidx.media3.common.Metadata;
@@ -30,7 +29,6 @@ import androidx.media3.exoplayer.FormatHolder;
 import androidx.media3.exoplayer.source.SampleStream.ReadDataResult;
 import androidx.media3.extractor.metadata.mp4.SlowMotionData;
 
-@RequiresApi(18)
 /* package */ final class TransformerAudioRenderer extends TransformerBaseRenderer {
 
   private static final String TAG = "TransformerAudioRenderer";
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerBaseRenderer.java b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerBaseRenderer.java
index 8703e29007..29bdce9048 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerBaseRenderer.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerBaseRenderer.java
@@ -19,7 +19,6 @@ package androidx.media3.transformer;
 import static androidx.media3.common.util.Assertions.checkStateNotNull;
 
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
 import androidx.media3.common.MimeTypes;
@@ -34,7 +33,6 @@ import org.checkerframework.checker.nullness.qual.EnsuresNonNullIf;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
-@RequiresApi(18)
 /* package */ abstract class TransformerBaseRenderer extends BaseRenderer {
 
   protected final MuxerWrapper muxerWrapper;
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerMediaClock.java b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerMediaClock.java
index a33b505502..82d5b45f55 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerMediaClock.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerMediaClock.java
@@ -18,12 +18,10 @@ package androidx.media3.transformer;
 import static androidx.media3.common.util.Util.minValue;
 
 import android.util.SparseLongArray;
-import androidx.annotation.RequiresApi;
 import androidx.media3.common.C;
 import androidx.media3.common.PlaybackParameters;
 import androidx.media3.exoplayer.MediaClock;
 
-@RequiresApi(18)
 /* package */ final class TransformerMediaClock implements MediaClock {
 
   private final SparseLongArray trackTypeToTimeUs;
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerVideoRenderer.java b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerVideoRenderer.java
index 0baca1b026..60d79eda20 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerVideoRenderer.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/TransformerVideoRenderer.java
@@ -20,7 +20,6 @@ import static androidx.media3.common.util.Assertions.checkNotNull;
 import static androidx.media3.exoplayer.source.SampleStream.FLAG_REQUIRE_FORMAT;
 
 import android.content.Context;
-import androidx.annotation.RequiresApi;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
 import androidx.media3.decoder.DecoderInputBuffer;
@@ -31,7 +30,6 @@ import java.nio.ByteBuffer;
 import org.checkerframework.checker.nullness.qual.MonotonicNonNull;
 import org.checkerframework.checker.nullness.qual.RequiresNonNull;
 
-@RequiresApi(18)
 /* package */ final class TransformerVideoRenderer extends TransformerBaseRenderer {
 
   private static final String TAG = "TransformerTranscodingVideoRenderer";
diff --git a/libraries/transformer/src/main/java/androidx/media3/transformer/VideoSamplePipeline.java b/libraries/transformer/src/main/java/androidx/media3/transformer/VideoSamplePipeline.java
index 1fe2bbe908..ac1f792dcd 100644
--- a/libraries/transformer/src/main/java/androidx/media3/transformer/VideoSamplePipeline.java
+++ b/libraries/transformer/src/main/java/androidx/media3/transformer/VideoSamplePipeline.java
@@ -21,7 +21,6 @@ import static androidx.media3.common.util.Assertions.checkNotNull;
 import android.content.Context;
 import android.media.MediaCodec;
 import androidx.annotation.Nullable;
-import androidx.annotation.RequiresApi;
 import androidx.media3.common.C;
 import androidx.media3.common.Format;
 import androidx.media3.common.PlaybackException;
@@ -33,7 +32,6 @@ import java.io.IOException;
 /**
  * Pipeline to decode video samples, apply transformations on the raw samples, and re-encode them.
  */
-@RequiresApi(18)
 /* package */ final class VideoSamplePipeline implements SamplePipeline {
 
   private static final String TAG = "VideoSamplePipeline";