diff --git a/src/Avalonia.Base/Input/Platform/BinaryFormatterHelper.cs b/src/Avalonia.Base/Input/Platform/BinaryFormatterHelper.cs
deleted file mode 100644
index 6e38a8afac..0000000000
--- a/src/Avalonia.Base/Input/Platform/BinaryFormatterHelper.cs
+++ /dev/null
@@ -1,72 +0,0 @@
-using System;
-using System.Diagnostics.CodeAnalysis;
-using System.IO;
-using System.Runtime.Serialization.Formatters.Binary;
-using Avalonia.Compatibility;
-using Avalonia.Logging;
-
-namespace Avalonia.Input.Platform;
-
-// TODO12: remove
-[Obsolete("Remove in v12")]
-internal static class BinaryFormatterHelper
-{
-    // Compatibility with WinForms + WPF...
-    private static ReadOnlySpan<byte> SerializedObjectGuid
-        => [
-            // FD9EA796-3B13-4370-A679-56106BB288FB
-            0x96, 0xa7, 0x9e, 0xfd,
-            0x13, 0x3b,
-            0x70, 0x43,
-            0xa6, 0x79, 0x56, 0x10, 0x6b, 0xb2, 0x88, 0xfb
-        ];
-
-    [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = "We still use BinaryFormatter for WinForms drag and drop compatibility")]
-    [UnconditionalSuppressMessage("Trimming", "IL3050", Justification = "We still use BinaryFormatter for WinForms drag and drop compatibility")]
-    public static byte[]? TrySerializeUsingBinaryFormatter(object data, DataFormat dataFormat)
-    {
-        if (!OperatingSystemEx.IsWindows())
-            return null;
-
-        Logger.TryGet(LogEventLevel.Warning, LogArea.Win32Platform)?.Log(
-            null,
-            "Using BinaryFormatter to serialize data format {Format}. This won't be supported in Avalonia v12. Prefer passing a byte[] or Stream instead.",
-            dataFormat);
-
-        var stream = new MemoryStream();
-        var serializedGuid = SerializedObjectGuid;
-
-#if NET6_0_OR_GREATER
-        stream.Write(serializedGuid);
-#else
-        stream.Write(serializedGuid.ToArray(), 0, serializedGuid.Length);
-#endif
-
-#pragma warning disable SYSLIB0011 // Type or member is obsolete
-        new BinaryFormatter().Serialize(stream, data);
-#pragma warning restore SYSLIB0011 // Type or member is obsolete
-
-        return stream.GetBuffer();
-    }
-
-    [UnconditionalSuppressMessage("Trimming", "IL2026", Justification = "We still use BinaryFormatter for WinForms drag and drop compatibility")]
-    [UnconditionalSuppressMessage("Trimming", "IL3050", Justification = "We still use BinaryFormatter for WinForms drag and drop compatibility")]
-    public static object? TryDeserializeUsingBinaryFormatter(byte[]? bytes)
-    {
-        var serializedObjectGuid = SerializedObjectGuid;
-
-        // Our Win32 backend used to automatically serialize/deserialize objects using the BinaryFormatter.
-        // Only keep that behavior for compatibility with IDataObject.
-        if (OperatingSystemEx.IsWindows() && bytes is not null && bytes.AsSpan().StartsWith(serializedObjectGuid))
-        {
-            using var stream = new MemoryStream(bytes);
-            stream.Position = serializedObjectGuid.Length;
-
-#pragma warning disable SYSLIB0011 // Type or member is obsolete
-            return new BinaryFormatter().Deserialize(stream);
-#pragma warning restore SYSLIB0011 // Type or member is obsolete
-        }
-
-        return null;
-    }
-}
diff --git a/src/Avalonia.Base/Input/Platform/Clipboard.cs b/src/Avalonia.Base/Input/Platform/Clipboard.cs
index 6810851775..0d961cde3e 100644
--- a/src/Avalonia.Base/Input/Platform/Clipboard.cs
+++ b/src/Avalonia.Base/Input/Platform/Clipboard.cs
@@ -75,9 +75,7 @@ internal sealed class Clipboard(IClipboardImpl clipboardImpl) : IClipboard
                 .ToArray();
         }
 
-        var typedFormat = DataFormat.CreateBytesPlatformFormat(format);
-        var bytes = await dataTransfer.TryGetValueAsync(typedFormat).ConfigureAwait(false);
-        return BinaryFormatterHelper.TryDeserializeUsingBinaryFormatter(bytes) ?? bytes;
+        return null;
     }
 
     public Task<IAsyncDataTransfer?> TryGetDataAsync()
diff --git a/src/Avalonia.Base/Input/Platform/DataObjectToDataTransferItemWrapper.cs b/src/Avalonia.Base/Input/Platform/DataObjectToDataTransferItemWrapper.cs
index 656fbce996..fad3716bc7 100644
--- a/src/Avalonia.Base/Input/Platform/DataObjectToDataTransferItemWrapper.cs
+++ b/src/Avalonia.Base/Input/Platform/DataObjectToDataTransferItemWrapper.cs
@@ -1,11 +1,8 @@
 using System;
 using System.Diagnostics;
-using System.Diagnostics.CodeAnalysis;
 using System.IO;
-using System.Runtime.Serialization.Formatters.Binary;
 using System.Text;
 using Avalonia.Compatibility;
-using Avalonia.Logging;
 
 namespace Avalonia.Input.Platform;
 
@@ -73,7 +70,7 @@ internal sealed class DataObjectToDataTransferItemWrapper(
                 return buffer;
 
             default:
-                return BinaryFormatterHelper.TrySerializeUsingBinaryFormatter(data, format);
+                return null;
         }
     }
 }
diff --git a/src/Avalonia.Base/Input/Platform/DataTransferToDataObjectWrapper.cs b/src/Avalonia.Base/Input/Platform/DataTransferToDataObjectWrapper.cs
index f1d6040efa..814adfc4ff 100644
--- a/src/Avalonia.Base/Input/Platform/DataTransferToDataObjectWrapper.cs
+++ b/src/Avalonia.Base/Input/Platform/DataTransferToDataObjectWrapper.cs
@@ -36,9 +36,7 @@ internal sealed class DataTransferToDataObjectWrapper(IDataTransfer dataTransfer
                 .ToArray();
         }
 
-        var typedFormat = DataFormat.CreateBytesPlatformFormat(dataFormat);
-        var bytes = DataTransfer.TryGetValue(typedFormat);
-        return BinaryFormatterHelper.TryDeserializeUsingBinaryFormatter(bytes) ?? bytes;
+        return null;
     }
 
 }