diff --git a/ui/app.py b/ui/app.py
index 8858981..cdc9215 100644
--- a/ui/app.py
+++ b/ui/app.py
@@ -157,7 +157,7 @@ def serve_video(video_id):
 
     for full_path in candidates:
         try:
-            return send_file(full_path, mimetype="video/mp4", conditional=True)
+            return send_file(full_path, conditional=True)
         except FileNotFoundError:
             continue
 
@@ -343,7 +343,7 @@ _REVIEW_TEMPLATE = """
         <h2>Video</h2>
         <div class="video-wrap">
             <video controls preload="metadata" id="review-video">
-                <source src="/video/{{ video.video_id }}" type="video/mp4">
+                <source src="/video/{{ video.video_id }}">
                 Video playback not supported.
             </video>
         </div>