How to Fix MP4 Won’t Open in QuickTime. 8 Effective Ways
Struggling with “MP4 won’t open in QuickTime error?” While QuickTime is default player for MP4 on Mac, it’s not without issues. Moreover, despite being a popular file format and industry standard, MP4 files may sometimes not open on QuickTime. The primary reason behind both of these issues is incompatibility between MP4 and QuickTime player. However, that’s not the sole reason.
So, why is MP4 not compatible with QuickTime, and what are other factors besides it causing “QuickTime player can’t open MP4 file” issue? We’ll share each reason and their solutions and also some tips to avoid QuickTime player being unable to open MP4 files in future. So, scroll down till the end!

Part 1: Why QuickTime Player Won’t Open MP4?
If you’re wondering, Why is MP4 not compatible with QuickTime and what are other reasons besides incompatibility, we’ve answered below. Check out what factors lead to “QuickTime being unable to open MP4 file:”
- Outdated QuickTime versions lack support for recent MP4 codecs.
- Bugs on Mac may affect MP4 playback in QuickTime.
- Corrupted MP4 files from issues like improper transfers or viruses can cause playback failures.
- Lack of required audio codec or system failures may impact playback on Mac.
- QuickTime media player is corrupted.
Part 2: 8 Ways to Fix MP4 Not Playing on Mac
Once you know reasons behind “QuickTime player can’t open MP4,” you can start fixing this problem on your Mac. One by one, try out the eight solutions below which range from basic to advanced until one of them resolves the issue:
2.1. Restart Your Mac
More often than not restarting your computer can fix “QuickTime player won’t open MP4” error. It might not solve all QuickTime problems, but it’s worth a shot. By restarting Mac you can clear out temporary glitches, residual data, or background programs causing “MP4 not compatible with QuickTime” issue. Here are steps to follow:
Hit “Apple” icon and choose “Restart” from menu. The system will shut down and restart after a short pause.
2.2. Repair Corrupted MP4 File
If “QuickTime player can’t open MP4” it could be caused by MP4 file corruption rather than an issue with player. If that’s the case, no solution will work except to fix damaged MP4 file with a file repair tool. 4DDiG File Repair Mac is an awesome tool to efficiently repair severely corrupted and unplayable video files from internal and external storage devices. Here’s a lowdown on this tool’s features:
- Fix damaged, distorted, fuzzy, unplayable, or grainy videos.
- Repair no sound or audio and video sync issues.
- Supports 3000+ video file types including popular formats like MP4, MOV, MKV, M4V, 3G2, and 3GP.
- Compatible with Mac-based internal and external storage devices.
- Supports batch repair of multiple videos of different formats at once.
Here’s how to use this tool to repair corrupted 4DDiG file on Mac:
Step 1: Download, install, and launch MP4 file repair tool on Mac. Then, select “Fix Video Errors” and hit “Start” to import corrupted MP4 file(s).
Step 2: Click “Repair” to start repairing unplayable MP4 file(s). Hit “View Results” to preview repaired MP4 file(s) after the scan has finished.
Step 3: Choose videos and click “Export Selected” to save them in “Finder” folder. Open QuickTime Player and check if repaired MP4 file(s) plays successfully without issues.
2.3. Update QuickTime Player
Sometimes, “MP4 won’t open in QuickTime” due to player being outdated. Therefore, updating it to latest version is key to resolving this issue. Check out instructions below to update QuickTime Player in two ways:
Step 1: Head to “QuickTime Player,” choose “Upgrade Now,” and follow prompts for any available updates. Afterward, check if it now plays MP4 files.
Step 2: Uninstall QuickTime, visit official download page, pick QuickTime version based on your current macOS, and install it.
2.4. Delete Recent and Cache Files
Even though Macs are usually stable, having too many recent and temporary files can cause an “MP4 Not Playing on Mac” issue. These files may not seem like a big deal. But when they add up, they take up important space on computer, slowing down QuickTime Player as a result. However, you can delete them with following steps:
2.4.1. Delete Temporary Files
Deleting temporary files releases much-needed memory for QuickTime player to run an MP4 file. It will also clear corrupted or outdated caches to resolve “QuickTime player won’t open MP4” issue. Here’s how to delete temp files on Mac:
Step 1: Close all apps, right-click on “Go,” head to “Finder,” and select “Folder.”
Step 2: Type “~/Library/Caches/” in search box and press “Go.”
Step 3: Check temporary files of specific apps, and delete them.
2.4.2. Delete Recent Files
You can disable Spotlight from indexing main hard drive to clear the Recents folder in macOS. But keep in mind, that this disables Spotlight temporarily, so you won’t be able to search for files and folders on hard drive. After doing this, recent items in Finder will be gone once Spotlight reindexes. Here’s how to delete recent files on Mac:
- Step 1: Head to “System Preferences,” and choose “Spotlight.”
- Step 2: Click “Privacy,” and press “+” button.
- Step 3: Add “Macintosh HD” to list and click “OK” to empty recent items.
2.5. Choose Another Media Player
The “MP4 not compatible with QuickTime” glitch could also happen if QuickTime player is corrupted. So, rather than opening an MP4 video on QuickTime choose to play file on another media player like VLC. This player offers an all-in-one solution for playing all popular and less common video and audio formats. You don’t need extra codecs or converters to use VLC. Other good options to play MP4 files on Mac are DivX Player, Real Player, and MPlayerX.
2.6. Check for Supported Codecs
If you get “MP4 not compatible with QuickTime” or “MP4 Not Playing on Mac” issue on Mac it could often happen due to codec issues. MP4 is basically a container for videos, audio, and metadata. If QuickTime Player can’t play an MP4 video, it’s likely because video is compressed using an incompatible codec.
To resolve this problem, either use a better media player that supports MP4 codec or convert video to a compatible one, like H.264. We suggest using MP4 with H.264 or H.265 for broad compatibility across devices and browsers. To know whether your MP4 file codecs match QuickTime check out instructions below:
Step 1: Play MP4 file in VLC. If it works, it means file is fine, and problem is with QuickTime’s codec support.
Step 2: Head to “Window,” in your opened MP4 file and select “Display Movie Inspector.”
Step 3: A window will pop up showing details like source, format, frame rates, size, data size, and data rate. Keep an eye on “Format” to see codecs.
2.7. Change MP4 File Extension
If you’re still thinking, “Why is MP4 not compatible with QuickTime,” you can change MP4 file extension to M4V. Here’s how:
Step 1: Copy original video in “Finder,” rename it, and change the extension from .MP4 to .M4V.
You’ll get a warning about opening in a different application—click “Use .m4v” to confirm.
Step 3: Play video in M4V format with your VLC player and see if it works to fix “QuickTime player can’t open MP4” error.
2.8. Convert MP4 File
You can also convert MP4 file to another compatible format by using VLC if QuickTime player won’t open MP4. Here’s how:
Step 1: Open “VLC,” click “File,” and choose “Convert / Stream.”
Step 2: Press “Open Media” to select MP4 video with issue for conversion.
Step 3: Choose a profile from drop-down menu, and customize format, video codec, audio codec, and subtitles. For example, select “Video – H.264 + MP3 (MP4)” and click “Customize” to choose compatible codecs for video and audio.
Step 4: At bottom, choose either to stream or convert MP4 video.
Step 5: Opt for “Save as File,” select an output location, and hit “Save.” Your unplayable MP4 video will be converted.
Part 3: Tips to Avoid MP4 File Not Opening in QuickTime
To prevent “MP4 Not Playing on Mac,” you need to take some preventive measures. Here are some tips to remember:
Update QuickTime Player – Make sure to update QuickTime Player regularly to benefit from latest bug fixes and improvements. This ensures its compatibility with MP4 files.
Install Compatible Codecs and Plugins – If QuickTime Player lacks required codecs or plugins for specific MP4 files, install them to ensure compatibility and seamless playback.
Download from Legitimate Sources – Stick to reliable websites and sources when downloading MP4 files. This minimizes chances of getting corrupt or incompatible files for QuickTime player.
Conclusion
If your MP4 won’t open in QuickTime, it’s due to compatibility issues between MP4 file and QuickTime player. But there are other reasons as well. The problem could come from an issue with QuickTime player or corruption in MP4 file.
If the issue is due to MP4 file corruption consider using 4DDiG File Repair to fix a variety of errors. This versatile tool excels in batch repairing multiple file formats simultaneously, ensuring a high success rate.