diff --git a/api/src/Sozsoft.Platform.Application/FileManagement/FileManagementAppService.cs b/api/src/Sozsoft.Platform.Application/FileManagement/FileManagementAppService.cs
index da57029..9171ccf 100644
--- a/api/src/Sozsoft.Platform.Application/FileManagement/FileManagementAppService.cs
+++ b/api/src/Sozsoft.Platform.Application/FileManagement/FileManagementAppService.cs
@@ -51,6 +51,34 @@ public class FileManagementAppService : ApplicationService, IFileManagementAppSe
 
     private string GetTenantPrefix(string tenantId) => $"tenants/{tenantId}/";
 
+    private static string NormalizeExtension(string? extensionOrFileName)
+    {
+        if (string.IsNullOrWhiteSpace(extensionOrFileName))
+        {
+            return string.Empty;
+        }
+
+        var ext = extensionOrFileName.Trim();
+
+        // If a path was provided, extract extension from the file name
+        if (ext.Contains('/') || ext.Contains('\\'))
+        {
+            ext = Path.GetExtension(ext);
+        }
+        else if (!ext.StartsWith('.') && ext.Contains('.'))
+        {
+            // File name like "photo.jpg" (but not an extension like ".jpg")
+            ext = Path.GetExtension(ext);
+        }
+
+        if (string.IsNullOrWhiteSpace(ext))
+        {
+            return string.Empty;
+        }
+
+        return ext.Trim().TrimStart('.').ToLowerInvariant();
+    }
+
     private string GetEffectiveTenantId(string? inputTenantId) =>
         !string.IsNullOrEmpty(inputTenantId) ? inputTenantId : (_currentTenant.Id?.ToString() ?? "host");
 
@@ -170,6 +198,8 @@ public class FileManagementAppService : ApplicationService, IFileManagementAppSe
                 var fileInfo = new FileInfo(file);
                 var relativePath = string.IsNullOrEmpty(folderPath) ? fileInfo.Name : $"{folderPath}/{fileInfo.Name}";
 
+                var normalizedExtension = NormalizeExtension(fileInfo.Extension);
+
                 items.Add(new FileMetadata
                 {
                     Id = EncodePathAsId(relativePath),
@@ -181,7 +211,9 @@ public class FileManagementAppService : ApplicationService, IFileManagementAppSe
                     Path = relativePath,
                     ParentId = folderPath ?? "",
                     IsReadOnly = false,
-                    TenantId = tenantId == "host" ? null : tenantId
+                    TenantId = tenantId == "host" ? null : tenantId,
+                    Extension = normalizedExtension,
+                    MimeType = GetMimeType(normalizedExtension)
                 });
             }
 
@@ -379,6 +411,7 @@ public class FileManagementAppService : ApplicationService, IFileManagementAppSe
         }
 
         var fileInfo = new FileInfo(uniqueFileName);
+        var normalizedExtension = NormalizeExtension(fileInfo.Extension);
 
         var metadata = new FileMetadata
         {
@@ -386,8 +419,8 @@ public class FileManagementAppService : ApplicationService, IFileManagementAppSe
             Name = uniqueFileName,
             Type = "file",
             Size = fileSize,
-            Extension = fileInfo.Extension,
-            MimeType = GetMimeType(fileInfo.Extension),
+            Extension = normalizedExtension,
+            MimeType = GetMimeType(normalizedExtension),
             CreatedAt = DateTime.UtcNow,
             ModifiedAt = DateTime.UtcNow,
             Path = filePath,
@@ -711,7 +744,7 @@ public class FileManagementAppService : ApplicationService, IFileManagementAppSe
                     File.Copy(sourceFullPath, uniqueTargetPath);
 
                     var fileInfo = new FileInfo(uniqueTargetPath);
-                    var extension = fileInfo.Extension;
+                    var extension = NormalizeExtension(fileInfo.Extension);
 
                     copiedItems.Add(new FileItemDto
                     {
@@ -839,7 +872,7 @@ public class FileManagementAppService : ApplicationService, IFileManagementAppSe
                     File.Move(sourceFullPath, uniqueTargetPath);
 
                     var fileInfo = new FileInfo(uniqueTargetPath);
-                    var extension = fileInfo.Extension;
+                    var extension = NormalizeExtension(fileInfo.Extension);
 
                     movedItems.Add(new FileItemDto
                     {
@@ -1013,7 +1046,16 @@ public class FileManagementAppService : ApplicationService, IFileManagementAppSe
 
     private string GetMimeType(string extension)
     {
-        return extension.ToLowerInvariant() switch
+        if (string.IsNullOrWhiteSpace(extension))
+        {
+            return "application/octet-stream";
+        }
+
+        var normalized = extension.Trim();
+        normalized = normalized.StartsWith('.') ? normalized : "." + normalized;
+        normalized = normalized.ToLowerInvariant();
+
+        return normalized switch
         {
             ".txt" => "text/plain",
             ".pdf" => "application/pdf",
diff --git a/ui/src/views/admin/files/components/FileItem.tsx b/ui/src/views/admin/files/components/FileItem.tsx
index 7ae2a47..aef54e8 100644
--- a/ui/src/views/admin/files/components/FileItem.tsx
+++ b/ui/src/views/admin/files/components/FileItem.tsx
@@ -324,6 +324,8 @@ const FileItem = forwardRef<HTMLDivElement, FileItemProps>((props, ref) => {
   const ImagePreview = ({ src, alt }: { src: string; alt: string }) => {
     const [imageError, setImageError] = useState(false)
 
+    console.log('Rendering ImagePreview with src:', src) // Debug için
+
     return (
       <div className="w-full h-full bg-gray-100 dark:bg-gray-700 rounded flex items-center justify-center overflow-hidden">
         {!imageError ? (
@@ -378,7 +380,7 @@ const FileItem = forwardRef<HTMLDivElement, FileItemProps>((props, ref) => {
           <div className="w-8 h-8">
             {item.type === 'file' && item.mimeType?.startsWith('image/') ? (
               <ImagePreview
-                src={`/api/app/file-management/${item.id}/download-file`}
+                src={FILE_URL(item.path, item.tenantId)}
                 alt={item.name}
               />
             ) : (
@@ -477,7 +479,7 @@ const FileItem = forwardRef<HTMLDivElement, FileItemProps>((props, ref) => {
         {item.type === 'file' && item.mimeType?.startsWith('image/') ? (
           <div className="w-16 h-16">
             <ImagePreview
-              src={`/api/app/file-management/${item.id}/download-file`}
+              src={FILE_URL(item.path, item.tenantId)}
               alt={item.name}
             />
           </div>