Mac's built-in media player - QuickTime Player is the default option when it comes to media playback for a lot of users. The player can play iTunes files that are protected by DRM encryption, which is an advantage that you don't get with regular media players. However, it seems that sometimes QuickTime Player can't open MP4 according to users' feedback. Is that the case? If yes, how to fix it when you can't open MP4 with QuickTime Player? Just read on.

Part 1: Is QuickTime Player Able to Open MP4?

QuickTime Player is the go-to option for Mac users. The player can handle a variety of digital formats, for instance, video, picture, sound, panoramic, etc. However, the popular media player doesn't seem to support MP4 format from time to time, and that's why people are reporting the "QuickTime Player can't open MP4" issue recently. It's frustrating as you naturally consider MP4 as a popular format that can be played on everything.

Of all the media formats out there, MP4 is the industry standard for video. It's also the most compatible format these days. Technically, the MPEG-4 format specification is based on the QuickTime format, hence QuickTime Player does support MP4 as one of the input formats. However, it seems QuickTime Player can open some MP4 files, but not all of them. How so? Just keep reading.

Part 2: Why QuickTime Player Can't Open MP4?

There can be multiple reasons that QuickTime Player can't open MP4. It could be just a glitch or a complicated cause. But it's worth noting that MP4 is a file format or container. You can imagine that it is like a box that has your video, audio, and metadata in. Here MP4 defines how the video, audio, and metadata are stored within the container.

Sometimes you can even swap out the container without changing the file type. The container format is completely different from the video format(video codec). MP4 can use various video and audio codecs, sometimes H.264 for video and AAC for audio, sometimes others. That's why sometimes your QuickTime Player can support MP4 playback, occasionally it doesn't.

Here's a complete list of QuickTime Supported Media formats.

Video Audio
File formats Codecs File formats Codecs
QuickTime Movie (.mov) MPEG-2 (OS X Lion or later) iTunes Audio (.m4a, .m4b, .m4p) AAC (MPEG-4 Audio)
MPEG-4 (.mp4, .m4v) MPEG-4 (Part 2) MP3 HE-AAC
MPEG-2 (OS X Lion or later) H.264 Core Audio (.caf) Apple Lossless
3GPP H.261 AU AMR Narrowband
3GPP2 Apple ProRes SD2 MS ADPCM
AVCHD (OS X Mountain Lion or later) Apple Pixlet WAV QDesign Music 2
AVI (Motion JPEG only) Animation SND Qualcomm PureVoice (QCELP)
DV Cinepak AMR IMA 4:1
Component Video MACE 3:1 (Mac OS X v10.6.x only)
DV MACE 6:1 (Mac OS X v10.6.x only)
DVC Pro 50 ALaw 2:1
Graphics ULaw 2:1
Motion JPEG 24-Bit Integer
Photo JPEG 32-Bit Integer
Sorenson Video 2 32-Bit Floating Point
Sorenson Video 3 64-Bit Floating Point

That is to say, when QuickTime Player can't open MP4, the video codec could be one of the obvious reasons. Generally speaking, the most commonly seen causes for the issue could be:

Corrupt file

Your MP4 file could be damaged or corrupted. It could be broken when you download it or got damaged when the media player paused unexpectedly. The MP4 file could also get damaged when it is copied from external devices. Regardless of the reasons, your QuickTime Player can't open MP4 when it is a corrupt file.

Software problem

It could be the bugs or glitches on your QuickTime Player. Is your QuickTime Player up to date? Just like the operating system, you will need to update QuickTime from time to time so it doesn't cause various errors or playback issues.

Codec compatibility

As mentioned earlier, the codec compatibility is largely relevant to MP4 playback. When your QuickTime can't open MP4, it could be the codec is not supported on QuickTime, hence, you might need to transcode the video to a compatible codec, or resort to a more powerful media player.

Part 3: Solutions to Issue 'QuickTime Player Can't Open MP4'

Now you see the differences between Container format and file codecs. So what can you do when QuickTime Player can't open MP4? Here are a few solutions that might help you out.

Fix 1. Restart QuickTime and computer

When QuickTime Player can't open MP4, let's start by ruling out glitches before everything else. This could be a quick fix to the issue. You can close the QuickTime Player and restart it to see if it helps. You can also restart your computer to try again.

Fix 2. Update QuickTime Player

You might want to update your QuickTime Player to the latest version to make sure everything works. To do so, you can check the current version of QuickTime Player by going to the menu QuickTime Player > About QuickTime Player. To update QuickTime, simply go to the App Store application on your Mac, and click on the Updates button. You can find all the apps that are available for update. Click on QuickTime and select "update."

Fix 3. Convert MP4 file

The simplest solution to the "QuickTime Player can't open MP4" issue is to fix the codec compatibility. As aforementioned, the video codecs in the MP4 file may not be supported on your QuickTime, so you might want to convert it to a compatible one, for instance, H. 264 or H.265 for better compatibility with various devices and media players. You can do the job with Leawo Video Converter, the most powerful converter on the block.

  • Leawo Video Converter
  • Leawo Video Converter

    1. Convert video and audio files between 180+ formats without quality loss
    2. Support 720P, 1080P and even real 4K video output
    3. Create photo slideshows from photos stored on camera, computer, camcorder, etc
    4. Built-in video editor to trim, crop, add watermark, apply special effect, etc
    5. 2D to 3D converter with 6 different 3D movie effects available

Leawo Video Converter is the ultimate solution to media editing. You can make video and audio conversion, burn videos and images to DVD/Blu-ray, as well as video and audio editing with it. With Leawo Video Converter, you can successfully make the file smaller without losing video quality. Apart from that, the converter could be a rarely seen program that can help you make your side-by-side 3D movies at home!

Fix 4. Change the codec

You can change the codec when QuickTime Player can't open MP4. Launch the player and click on the Windows > Show Movie Inspector to see a set of different codec options here. Switch to an alternative to see if it supports the MP4 playback.

Fix 5. Check corrupt file

If you suspect the MP4 file is corrupted and you can try a different media player to see if the issue is specific to QuickTime only. If the MP4 can't be opened with multiple media players, the file is likely corrupted or damaged. You can go with the VLC player to see if the MP4 can be played with it.

Fix 6. Get a new MP4 file

Your MP4 could have been damaged during transfer or download. If it's a downloaded file, try to get it again with a decent downloader.

Fix 7. Installing codecs

You can install the right codecs when QuickTime Player can't open MP4. Just go search the codecs and install them on your Mac. Please be aware that some codecs, particularly free ones from a wide variety of companies, might potentially cause more issues on your computer, making the case even worse to fix. So make sure you install codecs from trusted and authorized sources only.

Part 4: Best Alternative to QuickTime When QuickTime Player Can't Open MP4

When QuickTime Player can't open MP4, you can always go with a powerful video player to check the file. Here comes Leawo Blu-ray Player, the most professional media player that can play almost all the formats. Most importantly, it's free! Leawo Blu-ray Player is the best alternative to QuickTime Player and a serious competitor to VLC Media Player.

  • Leawo Blu-ray Player
  • Leawo Blu-ray Player

    Region-free Blu-ray player software to play Blu-ray disc and DVD disc for free, regardless of disc protection and region restriction.
    Play 4K FLV videos, 4K MKV videos, 4K MP4 videos, etc. without quality loss.
    Play 1080P videos, 720P videos with lossless quality.

With Leawo Blu-ray Player, you can play Blu-ray discs, DVDs, HD videos (4K), audio, BDAV movie folder, and Blu-ray ISO image files, and many more. You can check out the product page to see the countless formats it supports. Leawo Blu-ray Player is the best player for 4K Blu-ray. Unlike VLC supports unencrypted/region-free Blu-ray and DVD only, Leawo Blu-ray Player can play all Blu-ray and DVDs by breaking regional restrictions. It's the best choice if you want to avoid complicated decryption of all sorts.

Leawo Blu-ray Player can automatically recognize all the subtitle formats on your DVD or media files, and you can display the subtitles as a sidebar while watching. With Leawo Blu-ray Player, you can watch Korean dramas with English subtitles. Designed with a user-friendly interface, the player is intuitive to use. Simply launch the player and all your media files can play out of the box.

Final Thoughts

When QuickTime Player can't open MP4, simply identify the possible causes and apply the solutions above. If you find the MP4 can not be played properly because of codecs compatibility, then the simplest way to fix the issue is to use Leawo Video Converter. The converter supports 180+ formats, you can convert anything with the fastest speed possible! Meanwhile, try Leawo Blu-ray Player, the best alternative to VLC and QuickTime Player. If you are a fan of Blu-ray and hope to enjoy the best video quality with your collection, this is the player you don't want to miss.