diff --git a/frontend/src/components/PostEditForm.tsx b/frontend/src/components/PostEditForm.tsx
index 99039d9..5990c92 100644
--- a/frontend/src/components/PostEditForm.tsx
+++ b/frontend/src/components/PostEditForm.tsx
@@ -150,9 +150,52 @@ const PostEditForm: FC<Props> = ({ post, onSave }) => {
   const handleSubmit = async (e: FormEvent) => {
     e.preventDefault ()
 
+    if (disabled) return
+
     setDisabled (true)
     try
     {
+      const differences = [
+	  { name: label ('shared:labels.title'),
+	    prev: post.title ?? '', current: title ?? '' },
+	  { name: label ('shared:labels.parentPosts'),
+	    prev: (post.parentPosts ?? []).map (parent => parent.id).join (' '),
+	    current: parentPostIds },
+	  { name: label ('tags:title'),
+	    prev: tagsToStr (post.tags), current: tags },
+	  { name: label ('shared:labels.duration'),
+	    prev: videoMsToDurationValue (post.videoMs),
+	    current: videoFlg ? duration : '' },
+	  { name: <>{label ('shared:labels.originalCreatedAt')}{' '}
+		      {label ('shared:labels.since')}</>,
+	    prev: post.originalCreatedFrom ?? '', current: originalCreatedFrom ?? '' },
+	  { name: <>{label ('shared:labels.originalCreatedAt')}{' '}
+		      {label ('shared:labels.before')}</>,
+	    prev: post.originalCreatedBefore ?? '', current: originalCreatedBefore ?? '' }]
+	  .filter (row => row.prev !== row.current)
+
+      if (!(await dialogue.confirm ({
+	  title: label ('shared:actions.diff'),
+	  confirmText: label ('shared:actions.update'),
+	  description: (
+	      <dl className="max-h-[60dvh] overflow-y-auto space-y-3 text-left">
+		{differences.map ((row, index) => (
+		    <div key={index}>
+		      <dt className="font-semibold">{row.name}</dt>
+		      <dd className="whitespace-pre-wrap break-words">
+			{row.prev && (
+			    <del className="block text-red-600 dark:text-red-400">
+			      {row.prev}
+			    </del>)}
+			{row.current && (
+			    <ins className="block text-green-700 dark:text-green-400">
+			      {row.current}
+			    </ins>)}
+		      </dd>
+		    </div>))}
+	      </dl>) })))
+	return
+
       await update ({ id: post.id, title, tags, parentPostIds,
 		      duration: videoFlg ? duration : null,
 		      originalCreatedFrom, originalCreatedBefore },