How to open mp4 on Mac?

MP4 issues on Mac can be frustrating because they seem so random. One file plays perfectly, another one won’t open, and then there’s the classic case where there’s video but no sound. I’ve noticed that macOS tends to struggle when an MP4 uses non-standard encoding—especially certain audio formats. I usually keep Elmedia Player around; it doesn’t really care what’s inside the file, it just plays it. No guessing, no conversions, no digging through codec details.

If a file still refuses to cooperate, it might be worth trying Plex or Divx. Some players handle high-bitrate or variable frame rate MP4s better than others, and that can make a difference if the file stutters or won’t play smoothly. Also, some MP4s have multiple audio tracks, and not all players pick the right one by default—so if you’re getting a silent video, it’s worth checking if the player lets you switch tracks.

One thing people don’t always realize is that MP4 is just a container—it can hold H.264, HEVC, VP9, and even older MPEG variants, and not all of them are supported natively on macOS. If you’re dealing with an MP4 file that refuses to open no matter what, converting it to a more universal format like H.264/AAC can solve the problem. This is especially useful if you need to edit the file or use it across different Apple devices running macOS Sequoia.

Not all MP4 files are the same, and macOS doesn’t support every codec that can be packed into them.

Most of the time, when an MP4 file won’t open or plays without sound, it’s because the video or audio stream is using a codec that macOS doesn’t recognize. For example, macOS supports H.264 and HEVC (H.265) for video, but if the file is encoded with something older or less common, like an unusual MPEG-4 variant or VP9, it might not work. The same goes for audio - AAC is fine, but if the file uses DTS or AC3, you might get a silent video.

A quick way to check what’s inside the file is to open it with the built-in System Information tool (under the Apple menu > About This Mac > System Report > Media) or use a third-party file inspector to see the actual codecs. If the video is in an unsupported format, converting it to a more macOS-friendly codec like H.264/AAC is one option.

Another thing to watch out for is corrupted files. If an MP4 was only partially downloaded or encoded incorrectly, it might not open at all. You can sometimes test this by trying to play it on a different device - if it doesn’t work anywhere, chances are the file itself is the problem.

If you're running into this often, the simplest fix is to use a media player that supports a wider range of formats and codecs. macOS has built-in support for some, but not all, MP4 variations, and a good player will just open the file without making you think about what’s inside.

Blaskowitz wrote:

Ah, that makes sense now. So MP4 is just the container, and the “stuff inside” can be totally different—that explains why some files behave strangely. I didn’t realize audio tracks could be the culprit too. Sounds like checking the codec is really the key step.

You can check the video and audio codecs and their details with MediaInfo or Invisor.

Have you tried VLC? It supports most all mp4 formats.

Try VLC

You're welcome.