diff --git a/main.py b/main.py
index c6c0d93..4d5c52a 100644
--- a/main.py
+++ b/main.py
@@ -214,6 +214,51 @@ async def delete_book_api(book_id: int):
     return {"ok": ok, "message": message}
 
 
+_dedup_state: dict = {"running": False, "deleted": 0, "failed": 0, "total": 0, "done": False, "error": None}
+
+
+def _run_dedup():
+    global _dedup_state
+    try:
+        cfg = config.load()
+        log.info("Dedup: fetching all books ...")
+        books = fetch_all_books(cfg.calibre)
+        groups = find_duplicate_groups(books)
+        to_delete = [b for group in groups for b in sorted(group, key=lambda x: x.get("id", 0))[1:]]
+        _dedup_state.update({"total": len(to_delete), "deleted": 0, "failed": 0})
+        log.info("Dedup: %d duplicate(s) to delete across %d group(s)", len(to_delete), len(groups))
+        for book in to_delete:
+            ok, msg = delete_book(cfg.calibre, book["id"])
+            if ok:
+                _dedup_state["deleted"] += 1
+            else:
+                _dedup_state["failed"] += 1
+                log.warning("Dedup: failed to delete book %d: %s", book["id"], msg)
+            if _dedup_state["deleted"] % 10 == 0:
+                log.info("Dedup progress: %d / %d deleted", _dedup_state["deleted"], _dedup_state["total"])
+        log.info("Dedup done: %d deleted, %d failed", _dedup_state["deleted"], _dedup_state["failed"])
+    except Exception as e:
+        log.error("Dedup error: %s", e)
+        _dedup_state["error"] = str(e)
+    finally:
+        _dedup_state["running"] = False
+        _dedup_state["done"] = True
+
+
+@app.post("/api/delete_duplicates")
+async def delete_duplicates_api(background_tasks: BackgroundTasks):
+    if _dedup_state["running"]:
+        return {"ok": False, "message": "Already running"}
+    _dedup_state.update({"running": True, "deleted": 0, "failed": 0, "total": 0, "done": False, "error": None})
+    background_tasks.add_task(_run_dedup)
+    return {"ok": True, "message": "Started"}
+
+
+@app.get("/api/delete_duplicates/status")
+async def delete_duplicates_status():
+    return _dedup_state
+
+
 @app.get("/api/debug/calibre_books")
 async def debug_calibre_books():
     """Show raw Calibre-Web listbooks response shape so we can identify field names."""
diff --git a/templates/duplicates.html b/templates/duplicates.html
index 542ac3c..09afc6e 100644
--- a/templates/duplicates.html
+++ b/templates/duplicates.html
@@ -4,16 +4,23 @@
 {% block content %}
 <div class="page-header">
   <h1>Duplicate books in Calibre-Web</h1>
+  {% if groups %}
+  <div class="header-actions">
+    <button class="btn btn-danger" onclick="deleteAll(this)">Delete all duplicates (keep oldest)</button>
+  </div>
+  {% endif %}
 </div>
 
+<div id="dedup-progress" style="display:none" class="alert alert-success"></div>
+
 {% if error %}
   <div class="alert alert-warning">Could not fetch books from Calibre-Web: {{ error }}</div>
 {% else %}
   <p class="muted small" style="margin-bottom:1.5rem">
     Scanned <strong>{{ total_books }}</strong> book(s) —
     {% if groups %}
-      found <strong>{{ groups|length }}</strong> duplicate group(s).
-      Books are grouped by normalised title. Keep the one you want and delete the rest.
+      found <strong>{{ groups|length }}</strong> duplicate group(s) (same title + author).
+      The oldest copy (lowest ID) is kept when deleting all.
     {% else %}
       no duplicates found.
     {% endif %}
@@ -77,5 +84,41 @@ async function deleteBook(id, btn) {
     status.textContent = 'Error: ' + e;
   }
 }
+
+async function deleteAll(btn) {
+  if (!confirm('Delete all duplicates from Calibre-Web, keeping the oldest copy of each title+author? This cannot be undone.')) return;
+  btn.disabled = true;
+  btn.textContent = 'Starting…';
+  const progress = document.getElementById('dedup-progress');
+  progress.style.display = '';
+  progress.textContent = 'Fetching book list from Calibre-Web…';
+
+  await fetch('/api/delete_duplicates', {method: 'POST'});
+
+  const poll = setInterval(async () => {
+    const r = await fetch('/api/delete_duplicates/status');
+    const s = await r.json();
+    if (s.error) {
+      clearInterval(poll);
+      progress.textContent = 'Error: ' + s.error;
+      progress.className = 'alert alert-warning';
+      btn.disabled = false;
+      btn.textContent = 'Delete all duplicates (keep oldest)';
+      return;
+    }
+    if (s.total > 0) {
+      progress.textContent = `Deleting… ${s.deleted} / ${s.total} deleted, ${s.failed} failed`;
+    } else {
+      progress.textContent = 'Scanning for duplicates…';
+    }
+    if (s.done) {
+      clearInterval(poll);
+      progress.textContent = `Done — ${s.deleted} book(s) deleted, ${s.failed} failed. Reload to refresh the list.`;
+      btn.textContent = 'Reload';
+      btn.disabled = false;
+      btn.onclick = () => location.reload();
+    }
+  }, 2000);
+}
 </script>
 {% endblock %}
diff --git a/uploader.py b/uploader.py
index 2bcc79f..fdf1463 100644
--- a/uploader.py
+++ b/uploader.py
@@ -198,15 +198,16 @@ def delete_book(cfg: CalibreConfig, book_id: int) -> tuple[bool, str]:
 
 
 def find_duplicate_groups(books: list[dict]) -> list[list[dict]]:
-    """Group books by normalised title; return only groups with 2+ entries."""
+    """Group books by normalised title+author; return only groups with 2+ entries."""
     from collections import defaultdict
     groups: dict[str, list[dict]] = defaultdict(list)
     for book in books:
-        title = book.get("title", "")
-        # Normalise: lowercase, strip punctuation and extra whitespace — no word removal
-        key = re.sub(r"[^\w\s]", " ", title.lower())
-        key = re.sub(r"\s+", " ", key).strip()
-        if key:
+        title = re.sub(r"[^\w\s]", " ", book.get("title", "").lower())
+        title = re.sub(r"\s+", " ", title).strip()
+        authors = re.sub(r"[^\w\s]", " ", book.get("authors", "").lower())
+        authors = re.sub(r"\s+", " ", authors).strip()
+        key = f"{title}||{authors}"
+        if title:
             groups[key].append(book)
     return sorted(
         [g for g in groups.values() if len(g) > 1],