What to Do When Quicktime Player Can’t Open MP4 on Mac

Quicktime Player is a great multimedia software that allows you to enjoy all of your favorite video and audio files on a Mac. However, it’s not flawless. Just like every other piece of software, issues with performance and function can appear from time to time.

In this article, we’re going to take a look this issue: Quicktime Player can’t open an MP4 file. The issue can be caused by a few different reasons, and we’ll dive into how to fix this problem if it happens to you.

While an unresponsive MP4 can be annoying, it’s typically pretty easy to correct.

Why Won’t an MP4 File Open?

There’s no one exact reason why an MP4 file might not open for you in Quicktime Player. It could be as simple as a small, easy-to-fix glitch or as complicated as a completely corrupt file.

There are also other errors that can occur with software updates. Unless the file is completely corrupted, you can typically get things fixed pretty quickly.

Fix #1: Restart QuickTime and/or Your Mac

If you’re experiencing issues when opening an MP4 file, it’s a good idea to start with a small fix and work your way up from there. The first way to do that is by restarting the program and/or computer and seeing if it resolves the issue.

To restart your app, go to the Quit option from the drop-down menu in the top bar when Quicktime Player is open. Once the program is closed, wait a few moments and open it back up.

Then check to see if your MP4 file will open now. If it does, you’re all set. If not, continue reading for some other solutions.

The other quick-fix option is to restart your computer. That can often fix small technical issues that occur within a glitchy program or your operating system.

Fix #2: Update the Software

Sometimes, software incompatibilities or issues can be caused by outdated software. Everything may seem to be working just fine within your current version of Quicktime Player, but you can experience annoying issues like an MP4 file not opening up.

Updating the software can iron out such issues and get everything operating normally again.

You can check to see which version of Quicktime Player you are running by opening up the program and then selecting About Quicktime Player from the Quicktime Player menu in the top bar of your window.

That will open up a small window and show you what version you’re currently running.

If you happen to be running an outdated version of Quicktime Player you can update it quite easily. If you’re running the program on a Mac, go into the App Store application and then click on the updates button.

That will give you a list of all the installed applications and what updates they have available. Click on Quicktime Player and then select “update.”

Fix #3: Change the Codec

Another way to play an MP4 file when you encounter issues within Quicktime Player is to change the codec.

Sometimes a Mac will have issues when reading your MP4 file’s code. By changing it, you can get it to operate correctly.

To change the codec, start by opening up Quicktime Player. From there, click on the Window dropdown menu at the top of your screen. Scroll down and click on Show Movie Inspector.

You will see a set of different codec options here. Select an alternative one to see if that fixes the problem.

How to Check for a Corrupt MP4 File on Mac

If your MP4 file is completely corrupt, you may not be able to open it in Quicktime Player unless you salvage the data using a third-party software app or similar solution.

Even if you suspect that the file in question might be corrupted, you should always do a simple check to make sure that it doesn’t just experience issues in Quicktime itself.

To do that, close Quicktime Player and try to open your MP4 file in a different media player. If it works in a different platform, you know the issues are in Quicktime and not the file itself.

If the file doesn’t open in a different media player, attempt opening it again with a third media player. If all three of those attempts don’t lead to the proper results, there’s a decent chance the file is corrupted and in need of repair.


If you ever experience issues with opening an MP4 file within Quicktime Player on Mac, don’t panic. Typically, there are some easy solutions you can explore to resolve the issue and enjoy the video or audio contained within the file.

Follow the steps and suggestions above to narrow down the cause of the issue and be sure to check for updates to the software. Sometimes an easy fix is all it takes.

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