diff --git a/src/index.html b/src/index.html
index 44528c8..0a22b4b 100644
--- a/src/index.html
+++ b/src/index.html
@@ -1723,9 +1723,10 @@
           return [];
         }
 
-        // Build thumbnail URLs for all assets
+        // Immich's default thumbnail size is a 250px-wide WebP — too small for
+        // full-bleed portfolio cards. size=preview serves a ~1440px JPEG instead.
         const thumbnailUrls = assets.map(asset =>
-          `${baseUrl}/api/assets/${asset.id}/thumbnail?key=${shareKey}`
+          `${baseUrl}/api/assets/${asset.id}/thumbnail?key=${shareKey}&size=preview`
         );
 
         return thumbnailUrls;