diff --git a/backend/routes/admin.py b/backend/routes/admin.py
index b48720c..69dceeb 100644
--- a/backend/routes/admin.py
+++ b/backend/routes/admin.py
@@ -1058,21 +1058,25 @@ async def ors_stats(user=Depends(require_mod)):
 
 @router.post("/media/generate-previews")
 async def generate_media_previews(user=Depends(require_admin)):
-    """Generiert fehlende _preview.jpg für alle Bilder in /data/media."""
-    import io as _io
+    """Generiert fehlende _preview.webp für alle Bilder in /data/media."""
+    import logging as _log
     from media_utils import generate_preview, _PREVIEW_EXTS
+    _logger = _log.getLogger(__name__)
     MEDIA_DIR = os.getenv("MEDIA_DIR", "/data/media")
 
     generated = 0
     skipped   = 0
     errors    = 0
+    dirs_info = {}
 
     for subdir in ("diary", "forum", "breeds", "breeds/gallery", "breeds/submissions"):
         folder = os.path.join(MEDIA_DIR, subdir)
         if not os.path.isdir(folder):
+            dirs_info[subdir] = "not found"
             continue
-        for fname in os.listdir(folder):
-            # Nur Original-Bilder (keine _preview, _thumb, Videos, PDFs)
+        files = os.listdir(folder)
+        dirs_info[subdir] = f"{len(files)} files"
+        for fname in files:
             low = fname.lower()
             if "_preview" in low or "_thumb" in low:
                 continue
@@ -1091,10 +1095,13 @@ async def generate_media_previews(user=Depends(require_admin)):
                     generated += 1
                 else:
                     skipped += 1
+                    _logger.warning(f"Preview None für {subdir}/{fname}")
             except Exception as exc:
                 errors += 1
+                _logger.error(f"Preview-Fehler {subdir}/{fname}: {exc}")
 
-    return {"generated": generated, "skipped": skipped, "errors": errors}
+    _logger.info(f"generate-previews: {generated} neu, {skipped} vorhanden, {errors} Fehler | dirs: {dirs_info}")
+    return {"generated": generated, "skipped": skipped, "errors": errors, "dirs": dirs_info}
 
 
 # ------------------------------------------------------------------