diff --git a/src/Properties/Resources.resx b/src/Properties/Resources.resx
index 5d7f8f2..ce74a6b 100644
--- a/src/Properties/Resources.resx
+++ b/src/Properties/Resources.resx
@@ -193,4 +193,7 @@
   <data name="UnsupportedWebPFeature" xml:space="preserve">
     <value>The image uses a WebP feature that is not supported.</value>
   </data>
+  <data name="Lossless_Description" xml:space="preserve">
+    <value>Lossless</value>
+  </data>
 </root>
\ No newline at end of file
diff --git a/src/WebP/WebP.cpp b/src/WebP/WebP.cpp
index 2a0a4bb..6469c39 100644
--- a/src/WebP/WebP.cpp
+++ b/src/WebP/WebP.cpp
@@ -199,7 +199,7 @@ int __stdcall WebPSave(
     config.method = 6; // 6 is the highest quality encoding
     config.thread_level = 1;
 
-    if (encodeOptions->quality == 100)
+    if (encodeOptions->lossless)
     {
         config.lossless = 1;
         pic->use_argb = 1;
diff --git a/src/WebP/WebP.h b/src/WebP/WebP.h
index eeb6e58..af86150 100644
--- a/src/WebP/WebP.h
+++ b/src/WebP/WebP.h
@@ -41,6 +41,7 @@ typedef struct EncodeParams
 {
     float quality;
     int preset;
+    bool lossless;
 }EncParams;
 
 enum MetadataType
diff --git a/src/WebPFile.cs b/src/WebPFile.cs
index e0fef43..b9594e6 100644
--- a/src/WebPFile.cs
+++ b/src/WebPFile.cs
@@ -123,6 +123,9 @@ internal static unsafe Surface Load(byte[] webpBytes)
         /// <param name="output">The output Stream.</param>
         /// <param name="quality">The WebP save quality.</param>
         /// <param name="preset">The WebP encoding preset.</param>
+        /// <param name="lossless">
+        /// <see langword="true"/> if lossless encoding should be used; otherwise, <see langword="false"/>.
+        /// </param>
         /// <param name="scratchSurface">The scratch surface.</param>
         /// <param name="progressCallback">The progress callback.</param>
         /// <exception cref="FormatException">The image exceeds 16383 pixels in width and/or height.</exception>
@@ -133,6 +136,7 @@ internal static void Save(
             Stream output,
             int quality,
             WebPPreset preset,
+            bool lossless,
             Surface scratchSurface,
             ProgressEventHandler progressCallback)
         {
@@ -144,7 +148,8 @@ internal static void Save(
             WebPNative.EncodeParams encParams = new()
             {
                 quality = quality,
-                preset = preset
+                preset = preset,
+                lossless = lossless
             };
 
             scratchSurface.Clear();
diff --git a/src/WebPFileType.cs b/src/WebPFileType.cs
index cd02334..7154326 100644
--- a/src/WebPFileType.cs
+++ b/src/WebPFileType.cs
@@ -32,7 +32,8 @@ private enum PropertyNames
             Quality,
             KeepMetadata, // Obsolete, but retained to keep the value from being reused for a different property.
             ForumLink,
-            GitHubLink
+            GitHubLink,
+            Lossless
         }
 
         private readonly IWebPStringResourceManager strings;
@@ -201,6 +202,7 @@ public override PropertyCollection OnCreateSavePropertyCollection()
             {
                 StaticListChoiceProperty.CreateForEnum(PropertyNames.Preset, WebPPreset.Photo, false),
                 new Int32Property(PropertyNames.Quality, 95, 0, 100, false),
+                new BooleanProperty(PropertyNames.Lossless, false),
                 new UriProperty(PropertyNames.ForumLink, new Uri("https://forums.getpaint.net/topic/21773-webp-filetype/")),
                 new UriProperty(PropertyNames.GitHubLink, new Uri("https://github.com/0xC0000054/pdn-webp"))
             };
@@ -224,6 +226,9 @@ public override ControlInfo OnCreateSaveConfigUI(PropertyCollection props)
 
             info.SetPropertyControlValue(PropertyNames.Quality, ControlInfoPropertyNames.DisplayName, GetString("Quality_DisplayName"));
 
+            info.SetPropertyControlValue(PropertyNames.Lossless, ControlInfoPropertyNames.DisplayName, string.Empty);
+            info.SetPropertyControlValue(PropertyNames.Lossless, ControlInfoPropertyNames.Description, GetString("Lossless_Description"));
+
             PropertyControlInfo forumLinkPCI = info.FindControlForPropertyName(PropertyNames.ForumLink);
             forumLinkPCI.ControlProperties[ControlInfoPropertyNames.DisplayName].Value = GetString("ForumLink_DisplayName");
             forumLinkPCI.ControlProperties[ControlInfoPropertyNames.Description].Value = GetString("ForumLink_Description");
@@ -239,8 +244,9 @@ protected override void OnSaveT(Document input, Stream output, PropertyBasedSave
         {
             int quality = token.GetProperty<Int32Property>(PropertyNames.Quality).Value;
             WebPPreset preset = (WebPPreset)token.GetProperty(PropertyNames.Preset).Value;
+            bool lossless = token.GetProperty<BooleanProperty>(PropertyNames.Lossless).Value;
 
-            WebPFile.Save(input, output, quality, preset, scratchSurface, progressCallback);
+            WebPFile.Save(input, output, quality, preset, lossless, scratchSurface, progressCallback);
         }
     }
 }
diff --git a/src/WebPNative.cs b/src/WebPNative.cs
index aab761f..c6cc44c 100644
--- a/src/WebPNative.cs
+++ b/src/WebPNative.cs
@@ -71,6 +71,8 @@ internal sealed class EncodeParams
             public float quality;
             [MarshalAs(UnmanagedType.I4)]
             public WebPPreset preset;
+            [MarshalAs(UnmanagedType.U1)]
+            public bool lossless;
         }
 
         [StructLayout(LayoutKind.Sequential)]