diff --git a/streaming/output.py b/streaming/output.py
index c273bd1..1d820d5 100644
--- a/streaming/output.py
+++ b/streaming/output.py
@@ -181,6 +181,10 @@ class FileOutput(Output):
         if audio_source:
             cmd.extend(["-c:a", "aac", "-b:a", "192k", "-shortest"])
 
+        # Use fragmented mp4 for streamable output while writing
+        if str(self.path).endswith('.mp4'):
+            cmd.extend(["-movflags", "frag_keyframe+empty_moov+default_base_moof"])
+
         cmd.append(str(self.path))
 
         import sys