diff --git a/render.py b/render.py
index 4cd50e3..7415654 100644
--- a/render.py
+++ b/render.py
@@ -623,6 +623,7 @@ def render_all(options):
                 "-i", fragment_prefix / "front.mp4",
                 "-i", fragment_prefix / audio_front,
                 copy, "copy",
+                '-movflags', '+faststart',
                 fragment_prefix / "front-mixed.mp4",
             ])
             cmds.append([
@@ -631,6 +632,7 @@ def render_all(options):
                 "-i", fragment_prefix / "back.mp4",
                 "-i", fragment_prefix / audio_back,
                 "-c:v", "copy",
+                '-movflags', '+faststart',
                 fragment_prefix / "back-audio.mp4",
             ])
             for cmd in cmds: