diff --git a/src/ImageSharp/Advanced/AdvancedImageExtensions.cs b/src/ImageSharp/Advanced/AdvancedImageExtensions.cs
index 10267c8ef7..da0c7f60cf 100644
--- a/src/ImageSharp/Advanced/AdvancedImageExtensions.cs
+++ b/src/ImageSharp/Advanced/AdvancedImageExtensions.cs
@@ -27,7 +27,7 @@ public static class AdvancedImageExtensions
         Guard.NotNull(filePath, nameof(filePath));
 
         string ext = Path.GetExtension(filePath);
-        IImageFormat format = source.GetConfiguration().ImageFormatsManager.FindFormatByFileExtension(ext);
+        IImageFormat? format = source.GetConfiguration().ImageFormatsManager.FindFormatByFileExtension(ext);
         if (format is null)
         {
             StringBuilder sb = new();
@@ -40,7 +40,7 @@ public static class AdvancedImageExtensions
             throw new NotSupportedException(sb.ToString());
         }
 
-        IImageEncoder encoder = source.GetConfiguration().ImageFormatsManager.FindEncoder(format);
+        IImageEncoder? encoder = source.GetConfiguration().ImageFormatsManager.FindEncoder(format);
 
         if (encoder is null)
         {
diff --git a/src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs b/src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs
index 4957b7ba73..162c8ed399 100644
--- a/src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Bmp/BmpImageFormatDetector.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using System.Buffers.Binary;
 
@@ -15,7 +14,7 @@ public sealed class BmpImageFormatDetector : IImageFormatDetector
     public int HeaderSize => 2;
 
     /// <inheritdoc/>
-    public IImageFormat DetectFormat(ReadOnlySpan<byte> header)
+    public IImageFormat? DetectFormat(ReadOnlySpan<byte> header)
     {
         return this.IsSupportedFileFormat(header) ? BmpFormat.Instance : null;
     }
diff --git a/src/ImageSharp/Formats/Gif/GifImageFormatDetector.cs b/src/ImageSharp/Formats/Gif/GifImageFormatDetector.cs
index c826765009..db3d429046 100644
--- a/src/ImageSharp/Formats/Gif/GifImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Gif/GifImageFormatDetector.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 namespace SixLabors.ImageSharp.Formats.Gif;
 
@@ -13,7 +12,7 @@ public sealed class GifImageFormatDetector : IImageFormatDetector
     public int HeaderSize => 6;
 
     /// <inheritdoc/>
-    public IImageFormat DetectFormat(ReadOnlySpan<byte> header)
+    public IImageFormat? DetectFormat(ReadOnlySpan<byte> header)
     {
         return this.IsSupportedFileFormat(header) ? GifFormat.Instance : null;
     }
diff --git a/src/ImageSharp/Formats/IImageFormatDetector.cs b/src/ImageSharp/Formats/IImageFormatDetector.cs
index 17f565d2b2..e1bdc41f8f 100644
--- a/src/ImageSharp/Formats/IImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/IImageFormatDetector.cs
@@ -19,5 +19,5 @@ public interface IImageFormatDetector
     /// </summary>
     /// <param name="header">The <see cref="T:byte[]"/> containing the file header.</param>
     /// <returns>returns the mime type of detected otherwise returns null</returns>
-    IImageFormat DetectFormat(ReadOnlySpan<byte> header);
+    IImageFormat? DetectFormat(ReadOnlySpan<byte> header);
 }
diff --git a/src/ImageSharp/Formats/ImageDecoderUtilities.cs b/src/ImageSharp/Formats/ImageDecoderUtilities.cs
index 50635dbefb..2a5b91b094 100644
--- a/src/ImageSharp/Formats/ImageDecoderUtilities.cs
+++ b/src/ImageSharp/Formats/ImageDecoderUtilities.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using SixLabors.ImageSharp.IO;
 using SixLabors.ImageSharp.Memory;
diff --git a/src/ImageSharp/Formats/ImageFormatManager.cs b/src/ImageSharp/Formats/ImageFormatManager.cs
index dc09bb6a13..85424e7b8c 100644
--- a/src/ImageSharp/Formats/ImageFormatManager.cs
+++ b/src/ImageSharp/Formats/ImageFormatManager.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using System.Collections.Concurrent;
 
@@ -93,7 +92,7 @@ public class ImageFormatManager
     /// </summary>
     /// <param name="extension">The extension to discover</param>
     /// <returns>The <see cref="IImageFormat"/> if found otherwise null</returns>
-    public IImageFormat FindFormatByFileExtension(string extension)
+    public IImageFormat? FindFormatByFileExtension(string extension)
     {
         Guard.NotNullOrWhiteSpace(extension, nameof(extension));
 
@@ -110,7 +109,7 @@ public class ImageFormatManager
     /// </summary>
     /// <param name="mimeType">The mime-type to discover</param>
     /// <returns>The <see cref="IImageFormat"/> if found; otherwise null</returns>
-    public IImageFormat FindFormatByMimeType(string mimeType)
+    public IImageFormat? FindFormatByMimeType(string mimeType)
         => this.imageFormats.FirstOrDefault(x => x.MimeTypes.Contains(mimeType, StringComparer.OrdinalIgnoreCase));
 
     /// <summary>
@@ -160,11 +159,11 @@ public class ImageFormatManager
     /// </summary>
     /// <param name="format">The format to discover</param>
     /// <returns>The <see cref="IImageDecoder"/> if found otherwise null</returns>
-    public IImageDecoder FindDecoder(IImageFormat format)
+    public IImageDecoder? FindDecoder(IImageFormat format)
     {
         Guard.NotNull(format, nameof(format));
 
-        return this.mimeTypeDecoders.TryGetValue(format, out IImageDecoder decoder)
+        return this.mimeTypeDecoders.TryGetValue(format, out IImageDecoder? decoder)
             ? decoder
             : null;
     }
@@ -174,11 +173,11 @@ public class ImageFormatManager
     /// </summary>
     /// <param name="format">The format to discover</param>
     /// <returns>The <see cref="IImageEncoder"/> if found otherwise null</returns>
-    public IImageEncoder FindEncoder(IImageFormat format)
+    public IImageEncoder? FindEncoder(IImageFormat format)
     {
         Guard.NotNull(format, nameof(format));
 
-        return this.mimeTypeEncoders.TryGetValue(format, out IImageEncoder encoder)
+        return this.mimeTypeEncoders.TryGetValue(format, out IImageEncoder? encoder)
             ? encoder
             : null;
     }
diff --git a/src/ImageSharp/Formats/Jpeg/JpegImageFormatDetector.cs b/src/ImageSharp/Formats/Jpeg/JpegImageFormatDetector.cs
index 54e1b28ee3..3bf7346ff3 100644
--- a/src/ImageSharp/Formats/Jpeg/JpegImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Jpeg/JpegImageFormatDetector.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 namespace SixLabors.ImageSharp.Formats.Jpeg;
 
@@ -13,7 +12,7 @@ public sealed class JpegImageFormatDetector : IImageFormatDetector
     public int HeaderSize => 11;
 
     /// <inheritdoc/>
-    public IImageFormat DetectFormat(ReadOnlySpan<byte> header)
+    public IImageFormat? DetectFormat(ReadOnlySpan<byte> header)
         => this.IsSupportedFileFormat(header) ? JpegFormat.Instance : null;
 
     private bool IsSupportedFileFormat(ReadOnlySpan<byte> header)
diff --git a/src/ImageSharp/Formats/Pbm/PbmImageFormatDetector.cs b/src/ImageSharp/Formats/Pbm/PbmImageFormatDetector.cs
index 01ad9c62be..021cff2670 100644
--- a/src/ImageSharp/Formats/Pbm/PbmImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Pbm/PbmImageFormatDetector.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 namespace SixLabors.ImageSharp.Formats.Pbm;
 
@@ -17,7 +16,7 @@ public sealed class PbmImageFormatDetector : IImageFormatDetector
     public int HeaderSize => 2;
 
     /// <inheritdoc/>
-    public IImageFormat DetectFormat(ReadOnlySpan<byte> header) => IsSupportedFileFormat(header) ? PbmFormat.Instance : null;
+    public IImageFormat? DetectFormat(ReadOnlySpan<byte> header) => IsSupportedFileFormat(header) ? PbmFormat.Instance : null;
 
     private static bool IsSupportedFileFormat(ReadOnlySpan<byte> header)
     {
diff --git a/src/ImageSharp/Formats/Png/PngImageFormatDetector.cs b/src/ImageSharp/Formats/Png/PngImageFormatDetector.cs
index a389428070..2e20668248 100644
--- a/src/ImageSharp/Formats/Png/PngImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Png/PngImageFormatDetector.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using System.Buffers.Binary;
 
@@ -15,7 +14,7 @@ public sealed class PngImageFormatDetector : IImageFormatDetector
     public int HeaderSize => 8;
 
     /// <inheritdoc/>
-    public IImageFormat DetectFormat(ReadOnlySpan<byte> header)
+    public IImageFormat? DetectFormat(ReadOnlySpan<byte> header)
     {
         return this.IsSupportedFileFormat(header) ? PngFormat.Instance : null;
     }
diff --git a/src/ImageSharp/Formats/Tga/TgaImageFormatDetector.cs b/src/ImageSharp/Formats/Tga/TgaImageFormatDetector.cs
index 82246f3474..13d4e784c9 100644
--- a/src/ImageSharp/Formats/Tga/TgaImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Tga/TgaImageFormatDetector.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 namespace SixLabors.ImageSharp.Formats.Tga;
 
@@ -13,7 +12,7 @@ public sealed class TgaImageFormatDetector : IImageFormatDetector
     public int HeaderSize => 16;
 
     /// <inheritdoc/>
-    public IImageFormat DetectFormat(ReadOnlySpan<byte> header)
+    public IImageFormat? DetectFormat(ReadOnlySpan<byte> header)
     {
         return this.IsSupportedFileFormat(header) ? TgaFormat.Instance : null;
     }
diff --git a/src/ImageSharp/Formats/Tiff/TiffImageFormatDetector.cs b/src/ImageSharp/Formats/Tiff/TiffImageFormatDetector.cs
index c48014024f..9af6a659e3 100644
--- a/src/ImageSharp/Formats/Tiff/TiffImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Tiff/TiffImageFormatDetector.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 namespace SixLabors.ImageSharp.Formats.Tiff;
 
@@ -13,7 +12,7 @@ public sealed class TiffImageFormatDetector : IImageFormatDetector
     public int HeaderSize => 8;
 
     /// <inheritdoc/>
-    public IImageFormat DetectFormat(ReadOnlySpan<byte> header)
+    public IImageFormat? DetectFormat(ReadOnlySpan<byte> header)
     {
         if (this.IsSupportedFileFormat(header))
         {
diff --git a/src/ImageSharp/Formats/Webp/WebpImageFormatDetector.cs b/src/ImageSharp/Formats/Webp/WebpImageFormatDetector.cs
index 9b52492aaa..3b30a2cfb5 100644
--- a/src/ImageSharp/Formats/Webp/WebpImageFormatDetector.cs
+++ b/src/ImageSharp/Formats/Webp/WebpImageFormatDetector.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 namespace SixLabors.ImageSharp.Formats.Webp;
 
@@ -13,7 +12,7 @@ public sealed class WebpImageFormatDetector : IImageFormatDetector
     public int HeaderSize => 12;
 
     /// <inheritdoc />
-    public IImageFormat DetectFormat(ReadOnlySpan<byte> header)
+    public IImageFormat? DetectFormat(ReadOnlySpan<byte> header)
         => this.IsSupportedFileFormat(header) ? WebpFormat.Instance : null;
 
     private bool IsSupportedFileFormat(ReadOnlySpan<byte> header)
diff --git a/src/ImageSharp/Image.FromBytes.cs b/src/ImageSharp/Image.FromBytes.cs
index 2ea2b9d432..0d36e397c1 100644
--- a/src/ImageSharp/Image.FromBytes.cs
+++ b/src/ImageSharp/Image.FromBytes.cs
@@ -1,6 +1,5 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
 using SixLabors.ImageSharp.Formats;
 using SixLabors.ImageSharp.PixelFormats;
@@ -17,7 +16,7 @@ public abstract partial class Image
     /// </summary>
     /// <param name="data">The byte span containing encoded image data to read the header from.</param>
     /// <returns>The format or null if none found.</returns>
-    public static IImageFormat DetectFormat(ReadOnlySpan<byte> data)
+    public static IImageFormat? DetectFormat(ReadOnlySpan<byte> data)
         => DetectFormat(DecoderOptions.Default, data);
 
     /// <summary>
@@ -27,7 +26,7 @@ public abstract partial class Image
     /// <param name="data">The byte span containing encoded image data to read the header from.</param>
     /// <exception cref="ArgumentNullException">The options are null.</exception>
     /// <returns>The mime type or null if none found.</returns>
-    public static IImageFormat DetectFormat(DecoderOptions options, ReadOnlySpan<byte> data)
+    public static IImageFormat? DetectFormat(DecoderOptions options, ReadOnlySpan<byte> data)
     {
         Guard.NotNull(options, nameof(options.Configuration));
 
@@ -40,7 +39,7 @@ public abstract partial class Image
 
         foreach (IImageFormatDetector detector in configuration.ImageFormatsManager.FormatDetectors)
         {
-            IImageFormat f = detector.DetectFormat(data);
+            IImageFormat? f = detector.DetectFormat(data);
 
             if (f != null)
             {
diff --git a/src/ImageSharp/Image{TPixel}.cs b/src/ImageSharp/Image{TPixel}.cs
index 01dd727fc0..31fd015096 100644
--- a/src/ImageSharp/Image{TPixel}.cs
+++ b/src/ImageSharp/Image{TPixel}.cs
@@ -1,8 +1,6 @@
 // Copyright (c) Six Labors.
 // Licensed under the Six Labors Split License.
-#nullable disable
 
-using System.Buffers;
 using System.Runtime.CompilerServices;
 using System.Runtime.InteropServices;
 using SixLabors.ImageSharp.Advanced;
@@ -420,7 +418,7 @@ public sealed class Image<TPixel> : Image
     {
         Guard.NotNull(frames, nameof(frames));
 
-        ImageFrame<TPixel> rootFrame = frames.FirstOrDefault();
+        ImageFrame<TPixel>? rootFrame = frames.FirstOrDefault();
 
         if (rootFrame == null)
         {