diff --git a/src/lib/htmlUtils.ts b/src/lib/htmlUtils.ts
index b39a28f..9e4a3b6 100644
--- a/src/lib/htmlUtils.ts
+++ b/src/lib/htmlUtils.ts
@@ -17,9 +17,10 @@ const HTML_PATTERNS = {
 
 /**
  * Placeholder patterns for temporary replacement
+ * Using a format that's less likely to be modified by translation services
  */
-const PLACEHOLDER_PREFIX = "__DEEPLX_PRESERVE_";
-const PLACEHOLDER_SUFFIX = "__";
+const PLACEHOLDER_PREFIX = "ĦĐŁXĦ";
+const PLACEHOLDER_SUFFIX = "ĦĐŁXĦ";
 
 /**
  * Storage for preserved content during translation
@@ -39,7 +40,10 @@ function createPlaceholder(
   content: string,
   preserved: PreservedContent
 ): string {
-  const placeholder = `${PLACEHOLDER_PREFIX}${preserved.counter}${PLACEHOLDER_SUFFIX}`;
+  // Use a more unique format that's less likely to be translated
+  const placeholder = `${PLACEHOLDER_PREFIX}${preserved.counter
+    .toString()
+    .padStart(3, "0")}${PLACEHOLDER_SUFFIX}`;
   preserved.placeholders.set(placeholder, content);
   preserved.counter++;
   return placeholder;
@@ -93,12 +97,14 @@ export function restoreHtmlContent(
 ): string {
   let restoredText = translatedText;
 
-  // Restore all preserved content
+  // Restore all preserved content - handle case-insensitive matching
   for (const [placeholder, originalContent] of preserved.placeholders) {
-    restoredText = restoredText.replace(
-      new RegExp(placeholder, "g"),
-      originalContent
+    // Create case-insensitive regex to handle lowercase conversion
+    const regex = new RegExp(
+      placeholder.replace(/[.*+?^${}()|[\]\\]/g, "\\$&"),
+      "gi"
     );
+    restoredText = restoredText.replace(regex, originalContent);
   }
 
   // Additional cleanup: fix any remaining Chinese colons that might have been introduced
diff --git a/tests/lib/htmlUtils.test.ts b/tests/lib/htmlUtils.test.ts
index 0a2a083..3a8eb1d 100644
--- a/tests/lib/htmlUtils.test.ts
+++ b/tests/lib/htmlUtils.test.ts
@@ -36,7 +36,7 @@ describe("HTML Utils", () => {
       expect(processedText).not.toContain("</code>");
 
       // Should contain placeholders
-      expect(processedText).toContain("__DEEPLX_PRESERVE_");
+      expect(processedText).toContain("ĦĐŁXĦ");
 
       // Restore should bring back original content
       const restoredText = restoreHtmlContent(processedText, preserved);
@@ -49,7 +49,7 @@ describe("HTML Utils", () => {
 
       // The processed text should not contain colons
       expect(processedText).not.toContain(":");
-      expect(processedText).toContain("__DEEPLX_PRESERVE_");
+      expect(processedText).toContain("ĦĐŁXĦ");
 
       // Restore should bring back original colon
       const restoredText = restoreHtmlContent(processedText, preserved);
@@ -66,7 +66,7 @@ describe("HTML Utils", () => {
       expect(processedText).not.toContain(":");
 
       // Should contain placeholders
-      expect(processedText).toContain("__DEEPLX_PRESERVE_");
+      expect(processedText).toContain("ĦĐŁXĦ");
 
       // Restore should bring back all original content
       const restoredText = restoreHtmlContent(processedText, preserved);
@@ -92,6 +92,21 @@ describe("HTML Utils", () => {
       expect(restoredText).toContain("Hello: 世界:extra");
       expect(restoredText).not.toContain("：");
     });
+
+    it("should handle placeholders being converted to lowercase", () => {
+      const originalText = "<strong>A B </strong>";
+      const { processedText, preserved } = preserveHtmlContent(originalText);
+
+      // Simulate what happens when placeholders get converted to lowercase
+      const lowercasePlaceholders = processedText.toLowerCase();
+
+      const restoredText = restoreHtmlContent(lowercasePlaceholders, preserved);
+
+      // Should restore the original HTML tags correctly
+      expect(restoredText).toBe("<strong>a b </strong>");
+      expect(restoredText).toContain("<strong>");
+      expect(restoredText).toContain("</strong>");
+    });
   });
 
   describe("sanitizeHtmlContent", () => {