diff --git a/src/Beutl.Engine/Media/Decoding/IDecoderInfo.cs b/src/Beutl.Engine/Media/Decoding/IDecoderInfo.cs
index ce7dd64d4..5dccb849b 100644
--- a/src/Beutl.Engine/Media/Decoding/IDecoderInfo.cs
+++ b/src/Beutl.Engine/Media/Decoding/IDecoderInfo.cs
@@ -8,7 +8,7 @@ public interface IDecoderInfo
 
     bool IsSupported(string file)
     {
-        return VideoExtensions().Concat(AudioExtensions()).Contains(Path.GetExtension(file));
+        return VideoExtensions().Concat(AudioExtensions()).Contains(Path.GetExtension(file), StringComparer.OrdinalIgnoreCase);
     }
 
     IEnumerable<string> VideoExtensions();
diff --git a/src/Beutl.Engine/Media/Encoding/IEncoderInfo.cs b/src/Beutl.Engine/Media/Encoding/IEncoderInfo.cs
index f3ccb5002..5a957ed34 100644
--- a/src/Beutl.Engine/Media/Encoding/IEncoderInfo.cs
+++ b/src/Beutl.Engine/Media/Encoding/IEncoderInfo.cs
@@ -9,7 +9,7 @@ public interface IEncoderInfo
 
     bool IsSupported(string file)
     {
-        return SupportExtensions().Contains(Path.GetExtension(file));
+        return SupportExtensions().Contains(Path.GetExtension(file), StringComparer.OrdinalIgnoreCase);
     }
 
     IEnumerable<string> SupportExtensions();
diff --git a/src/Beutl/Services/PrimitiveImpls/SceneEditorExtension.cs b/src/Beutl/Services/PrimitiveImpls/SceneEditorExtension.cs
index 6e1befd7b..1f1fba224 100644
--- a/src/Beutl/Services/PrimitiveImpls/SceneEditorExtension.cs
+++ b/src/Beutl/Services/PrimitiveImpls/SceneEditorExtension.cs
@@ -49,7 +49,7 @@ public sealed class SceneEditorExtension : EditorExtension
 
     public override bool TryCreateEditor(string file, [NotNullWhen(true)] out Control? editor)
     {
-        if (file.EndsWith($".{Constants.SceneFileExtension}"))
+        if (file.EndsWith($".{Constants.SceneFileExtension}", StringComparison.OrdinalIgnoreCase))
         {
             editor = new EditView();
             return true;
@@ -63,7 +63,7 @@ public override bool TryCreateEditor(string file, [NotNullWhen(true)] out Contro
 
     public override bool TryCreateContext(string file, [NotNullWhen(true)] out IEditorContext? context)
     {
-        if (file.EndsWith($".{Constants.SceneFileExtension}")
+        if (file.EndsWith($".{Constants.SceneFileExtension}", StringComparison.OrdinalIgnoreCase)
             && ProjectItemContainer.Current.TryGetOrCreateItem(file, out Scene? model))
         {
             context = new EditViewModel(model);
@@ -88,6 +88,6 @@ public override FilePickerFileType GetFilePickerFileType()
 
     public override bool MatchFileExtension(string ext)
     {
-        return ext is ".scene";
+        return ext.Equals(".scene", StringComparison.OrdinalIgnoreCase);
     }
 }
diff --git a/src/Beutl/Services/PrimitiveImpls/SceneOutputExtension.cs b/src/Beutl/Services/PrimitiveImpls/SceneOutputExtension.cs
index 85fb001fd..0a091f98e 100644
--- a/src/Beutl/Services/PrimitiveImpls/SceneOutputExtension.cs
+++ b/src/Beutl/Services/PrimitiveImpls/SceneOutputExtension.cs
@@ -41,7 +41,7 @@ public override FilePickerFileType GetFilePickerFileType()
 
     public override bool MatchFileExtension(string ext)
     {
-        return ext is ".scene";
+        return string.Equals(ext, ".scene", StringComparison.OrdinalIgnoreCase);
     }
 
     public override bool TryCreateContext(IEditorContext editorContext, [NotNullWhen(true)] out IOutputContext? context)
diff --git a/src/Beutl/Services/PrimitiveImpls/SceneWorkspaceItemExtension.cs b/src/Beutl/Services/PrimitiveImpls/SceneWorkspaceItemExtension.cs
index c602745da..9e387016c 100644
--- a/src/Beutl/Services/PrimitiveImpls/SceneWorkspaceItemExtension.cs
+++ b/src/Beutl/Services/PrimitiveImpls/SceneWorkspaceItemExtension.cs
@@ -46,13 +46,13 @@ public override FilePickerFileType GetFilePickerFileType()
 
     public override bool IsSupported(string file)
     {
-        return file.EndsWith($".{Constants.SceneFileExtension}");
+        return file.EndsWith($".{Constants.SceneFileExtension}", StringComparison.OrdinalIgnoreCase);
     }
 
     public override bool TryCreateItem(string file, [NotNullWhen(true)] out ProjectItem? result)
     {
         result = null;
-        if (file.EndsWith($".{Constants.SceneFileExtension}"))
+        if (file.EndsWith($".{Constants.SceneFileExtension}", StringComparison.OrdinalIgnoreCase))
         {
             Scene? scene;
             try
diff --git a/src/Beutl/ViewModels/EditViewModel.cs b/src/Beutl/ViewModels/EditViewModel.cs
index 55e7a2c0e..5429fab53 100644
--- a/src/Beutl/ViewModels/EditViewModel.cs
+++ b/src/Beutl/ViewModels/EditViewModel.cs
@@ -553,6 +553,7 @@ Element CreateElementFor<T>(out T t)
 
     private static bool MatchFileExtensions(string filePath, IEnumerable<string> extensions)
     {
+        string ext = Path.GetExtension(filePath);
         return extensions
             .Select(x =>
             {
@@ -562,7 +563,7 @@ private static bool MatchFileExtensions(string filePath, IEnumerable<string> ext
                 else
                     return x;
             })
-            .Any(filePath.EndsWith);
+            .Contains(ext, StringComparer.OrdinalIgnoreCase);
     }
 
     private static bool MatchFileAudioOnly(string filePath)
diff --git a/src/Beutl/Views/EditorHostFallback.axaml.cs b/src/Beutl/Views/EditorHostFallback.axaml.cs
index f83673ca4..1b8535cd7 100644
--- a/src/Beutl/Views/EditorHostFallback.axaml.cs
+++ b/src/Beutl/Views/EditorHostFallback.axaml.cs
@@ -163,7 +163,7 @@ private void OpenRecentFile(string fileName)
 
             try
             {
-                if (fileName.EndsWith($".{Constants.ProjectFileExtension}"))
+                if (fileName.EndsWith($".{Constants.ProjectFileExtension}", StringComparison.OrdinalIgnoreCase))
                 {
                     viewModel.MenuBar.OpenRecentProject.Execute(fileName);
                 }
@@ -220,8 +220,8 @@ private void InitRecentItems()
         viewConfig.RecentFiles.ToObservableChangeSet<CoreList<string>, string>()
             .Filter(filter.Select<int, Func<string, bool>>(
                 f => (x) => f == 0
-                        || (f == 1 && x.EndsWith($".{Constants.ProjectFileExtension}"))
-                        || (f == 2 && !x.EndsWith($".{Constants.ProjectFileExtension}"))))
+                        || (f == 1 && x.EndsWith($".{Constants.ProjectFileExtension}", StringComparison.OrdinalIgnoreCase))
+                        || (f == 2 && !x.EndsWith($".{Constants.ProjectFileExtension}", StringComparison.OrdinalIgnoreCase))))
             .AddKey(x => x)
             .Cast(x => new FileInfo(x))
             .SortBy(x => x.LastAccessTimeUtc, sortOrder: SortDirection.Descending)