diff --git a/web/src/components/MemoEditor/index.tsx b/web/src/components/MemoEditor/index.tsx
index 9d6bfcd20..2aaee3971 100644
--- a/web/src/components/MemoEditor/index.tsx
+++ b/web/src/components/MemoEditor/index.tsx
@@ -54,9 +54,7 @@ const MemoEditorImpl: React.FC<MemoEditorProps> = ({
   const { userGeneralSetting } = useAuth();
 
   // Get default visibility from user settings
-  const defaultVisibility = userGeneralSetting?.memoVisibility
-    ? convertVisibilityFromString(userGeneralSetting.memoVisibility)
-    : undefined;
+  const defaultVisibility = userGeneralSetting?.memoVisibility ? convertVisibilityFromString(userGeneralSetting.memoVisibility) : undefined;
 
   useMemoInit(editorRef, memoName, cacheKey, currentUser?.name ?? "", autoFocus, defaultVisibility);
 
diff --git a/web/src/components/MemoView/components/metadata/AttachmentCard.tsx b/web/src/components/MemoView/components/metadata/AttachmentCard.tsx
index ce0efe758..2aadfb76c 100644
--- a/web/src/components/MemoView/components/metadata/AttachmentCard.tsx
+++ b/web/src/components/MemoView/components/metadata/AttachmentCard.tsx
@@ -1,6 +1,6 @@
 import { cn } from "@/lib/utils";
 import type { Attachment } from "@/types/proto/api/v1/attachment_service_pb";
-import { getAttachmentType, getAttachmentUrl, getColorspace } from "@/utils/attachment";
+import { getAttachmentType, getAttachmentUrl } from "@/utils/attachment";
 
 interface AttachmentCardProps {
   attachment: Attachment;
@@ -25,14 +25,7 @@ const AttachmentCard = ({ attachment, onClick, className }: AttachmentCardProps)
   }
 
   if (attachmentType === "video/*") {
-    return (
-      <video
-        src={sourceUrl}
-        className={cn("w-full h-full object-cover rounded-lg", className)}
-        controls
-        preload="metadata"
-      />
-    );
+    return <video src={sourceUrl} className={cn("w-full h-full object-cover rounded-lg", className)} controls preload="metadata" />;
   }
 
   return null;
diff --git a/web/src/components/MemoView/components/metadata/AttachmentList.tsx b/web/src/components/MemoView/components/metadata/AttachmentList.tsx
index 7783725fc..c60db187f 100644
--- a/web/src/components/MemoView/components/metadata/AttachmentList.tsx
+++ b/web/src/components/MemoView/components/metadata/AttachmentList.tsx
@@ -131,7 +131,6 @@ const AttachmentList = ({ attachments }: AttachmentListProps) => {
         onOpenChange={(open: boolean) => setPreviewImage((prev) => ({ ...prev, open }))}
         imgUrls={previewImage.urls}
         initialIndex={previewImage.index}
-        mimeType={previewImage.mimeType}
       />
     </>
   );
diff --git a/web/src/components/PreviewImageDialog.tsx b/web/src/components/PreviewImageDialog.tsx
index 9bcf424ca..4787c892e 100644
--- a/web/src/components/PreviewImageDialog.tsx
+++ b/web/src/components/PreviewImageDialog.tsx
@@ -2,19 +2,16 @@ import { X } from "lucide-react";
 import React, { useEffect, useState } from "react";
 import { Button } from "@/components/ui/button";
 import { Dialog, DialogContent } from "@/components/ui/dialog";
-import { getColorspace } from "@/utils/attachment";
 
 interface Props {
   open: boolean;
   onOpenChange: (open: boolean) => void;
   imgUrls: string[];
   initialIndex?: number;
-  mimeType?: string; // MIME type for HDR detection
 }
 
-function PreviewImageDialog({ open, onOpenChange, imgUrls, initialIndex = 0, mimeType }: Props) {
+function PreviewImageDialog({ open, onOpenChange, imgUrls, initialIndex = 0 }: Props) {
   const [currentIndex, setCurrentIndex] = useState(initialIndex);
-  const colorspace = mimeType ? getColorspace(mimeType) : undefined;
 
   // Update current index when initialIndex prop changes
   useEffect(() => {
@@ -83,7 +80,6 @@ function PreviewImageDialog({ open, onOpenChange, imgUrls, initialIndex = 0, mim
             draggable={false}
             loading="eager"
             decoding="async"
-            {...(colorspace && { colorSpace: colorspace as unknown as string })}
           />
         </div>
 
diff --git a/web/src/components/Settings/PreferencesSection.tsx b/web/src/components/Settings/PreferencesSection.tsx
index 126cda062..7d137fe34 100644
--- a/web/src/components/Settings/PreferencesSection.tsx
+++ b/web/src/components/Settings/PreferencesSection.tsx
@@ -82,10 +82,7 @@ const PreferencesSection = () => {
 
       <SettingGroup title={t("setting.preference")} showSeparator>
         <SettingRow label={t("setting.preference-section.default-memo-visibility")}>
-          <Select
-            value={setting.memoVisibility || "PRIVATE"}
-            onValueChange={handleDefaultMemoVisibilityChanged}
-          >
+          <Select value={setting.memoVisibility || "PRIVATE"} onValueChange={handleDefaultMemoVisibilityChanged}>
             <SelectTrigger className="min-w-fit">
               <div className="flex items-center gap-2">
                 <VisibilityIcon visibility={convertVisibilityFromString(setting.memoVisibility)} />
diff --git a/web/src/utils/attachment.ts b/web/src/utils/attachment.ts
index d78f04cf5..5f3f1c64e 100644
--- a/web/src/utils/attachment.ts
+++ b/web/src/utils/attachment.ts
@@ -52,34 +52,3 @@ export const isMidiFile = (mimeType: string): boolean => {
 const isPSD = (t: string) => {
   return t === "image/vnd.adobe.photoshop" || t === "image/x-photoshop" || t === "image/photoshop";
 };
-
-// HDR-capable MIME types that support wide color gamut
-export const HDR_CAPABLE_FORMATS = [
-  "image/heic",
-  "image/heif",
-  "image/webp",
-  "image/png", // PNG can contain ICC profiles for wide gamut
-  "image/jpeg", // JPEG can support extended color via profiles
-  "video/mp4", // Can contain HDR tracks
-  "video/quicktime", // Can contain HDR tracks
-  "video/x-matroska", // Can contain HDR tracks
-  "video/webm", // VP9 Profile 2 for HDR
-];
-
-// isHDRCapable returns true if the MIME type supports HDR/wide color gamut.
-export const isHDRCapable = (mimeType: string): boolean => {
-  return HDR_CAPABLE_FORMATS.some((format) => mimeType.startsWith(format));
-};
-
-// getColorspace returns the appropriate colorspace attribute for wide gamut images.
-// Returns "display-p3" for HDR-capable formats, undefined for standard images.
-export const getColorspace = (mimeType: string): string | undefined => {
-  return isHDRCapable(mimeType) ? "display-p3" : undefined;
-};
-
-// supportsHDR checks if the browser supports wide color gamut display.
-// Uses CSS.supports() to detect color-gamut capability.
-export const supportsHDR = (): boolean => {
-  if (typeof CSS === "undefined") return false;
-  return CSS.supports("(color-gamut: srgb)") && CSS.supports("(color-gamut: p3)");
-};