QuickTime Player can’t open or play MP4 on Mac?

Failed to open a MP4 file on Mac? MP4 video is not compatible with QuickTime Player?

QuickTime Player can't open or play MP4 on Mac?

We all know that MP4 is the industry standard, the most popular video format and QuickTime Player is the default app to open and play MP4 files on Mac. But why the QuickTime Player can play some MP4 files, not others.


Why MP4 videos can’t be opened or played on Mac?

MP4 is just a file format or container. It is like a box that contains your video, audio, and metadata. If the QuickTime Player won’t play a MP4 video, most likely the video is compressed using an incompatible codec. In such case, you can either use a more powerful media player with the codec support or transcode the video to a compatible codec, such as H.264. We recommend MP4 with h.264 or h.265 codec for great compatibility with various devices and even online browsers.

QuickTime Player video support

QuickTime Player can play various video formats like:
  • QuickTime Movie (.mov)
  • MPEG-4 (.mp4, .m4v)
  • MPEG-1
  • 3GPP
  • 3GPP2
  • AVI
  • DV
  • ....
In a wide range of codecs such as 
  • MPEG-4 (Part 2)
  • H.265
  • H.264
  • H.263
  • H.261
  • Apple ProRes
  • Apple Pixlet
  • Animation
  • Cinepak
  • Component Video
  • DV
  • DVC Pro
  • Graphics
  • Motion JPEG
  • Photo JPEG
  • Sorenson Video 2
  • Sorenson Video 3
  • ....

Change extension from .MP4 to .M4V – a quick fix

It may not always work. Just give it a try see if any luck when you found a MP4 video can’t be opened in QuickTime Player on Mac. Duplicate the original video file in Finder, then rename it and change its extension from .MP4 to .M4V.

You’ll be asked whether you are sure to change the extension from .mp4 to .m4v, if you make this change, your document may open in a different application. Click Use .m4v to confirm. Go to play the video in m4v format using the player you prefer see if any luck.

Find out video codec on Mac – optional

Want to know which codec the MP4 file is encoded with? Here’s the quick way to find out the video code on Mac. Find the video clip in Finder. Right-click (or press and hold Control key while you click) on the MP4 video file. Then choose Get Info option from the contextual menu. The file information dialog opens. Go to the More info section, you can see codecs of both audio and video used in the file.

Mac finder view video information audio video codecs

Note that this method may not work since the video in problem is not in a compatible format with the default media player on your Mac.

Get the free video player & converter

VLC media player is a free option you may consider. You should be able to download this free media player for Mac, then play most videos right away. What’s more, it even allows users the ability to transcode their videos to be compatible with a wide variety of devices and players.

vlc media player logo

Go to play the MP4 video in VLC Player first to make sure this media player can decode the video file in problem. You may find VLC is more powerful and user-friendly than QuickTime. In fact, people prefer VLC to QuickTime. If you still like to play the mp4 file in QuickTime, follow below instructions to convert it with VLC on your Mac.

View video codec in VLC player – optional

Many media players have embedded such a codec inspector so you can directly check video codec while playing a video file. Go to Window > Media Information to view the codec and other technical specifications.

vlc for Mac view codec details from media information

Convert videos using VLC media player on Mac

Here’s the quick steps to convert videos using VLC media player on Mac.

Launch VLC player on Mac. Click File > Convert / Stream …. from the top menu bar to open a new dialog as below.

vlc media player for Mac convert & stream tool

Click Open media button to find and open the video you like to convert in the VLC converter. Choose a profile from the drop-down menu and customize the format, video codec, audio codec, and subtitles. You can choose Video – H.264 + MP3 (MP4) as the profile, then click Customize button to choose the compatible codec for both video and audio as follows.

  • Video codec: you can choose H.264 or other compatible codec
  • Audio codec: MPEG 4 Audio (AAC) or other compatible codec

At the bottom of this Convert & Stream window, you can choose either to stream or convert the source video. Choose Save as File, click Browse to choose an output location. Finally hit the Save button to transcode your video. The Convert & Stream window disappears and you will be taken back to the main VLC media player window with the selected video added to the Playlist. Your video will be converted instantly and you can see the process bar at the bottom.

When finished, open the output folder to find the converted MP4 video file and play it with QuickTime Player on your Mac.

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