Posted by Candice Liu to QuickTime, MOV | Updated on Dec 6, 2018
QuickTime contains popular codecs such as MPEG4, H.264, DV and JPEG. But downloading additional codecs is deemed as indispensable to make up for the missing ones and have the videos under the compatible formats with QuickTime. Just check out our top list of QuickTime codec you have to download and install to expand QuickTime supported format lists, if you are subject to following playback issues.
![Movie Movie](/uploads/1/2/5/8/125865548/184299011.jpg)
The QuickTime web browser plug-in is no longer installed by default and is removed if you have a previous version of QuickTime on your PC. If you still need this legacy plug-in, you can add it back using the custom setup option in the installer. QuickTime 7 is for use with Windows Vista or Windows 7.
1. QuickTime shows you an error message when playing a file with unsupported media: 'The document could not be opened. A required codec isn't available.'
2. After you upgrade to macOS Sierra, you are unable to play MOV files and informed of a message 'Additional software is required for QuickTime to playback this media.' This is because Sierra deleted the QuickTimeMPEG2.component file from /Library/QuickTime.
3. You get a message 'The document could not be opened. The movie's file format isn't recognized' when playing AVI in QuickTime, just because the file is corrupt or a video/audio codec is mission.
2. After you upgrade to macOS Sierra, you are unable to play MOV files and informed of a message 'Additional software is required for QuickTime to playback this media.' This is because Sierra deleted the QuickTimeMPEG2.component file from /Library/QuickTime.
3. You get a message 'The document could not be opened. The movie's file format isn't recognized' when playing AVI in QuickTime, just because the file is corrupt or a video/audio codec is mission.
Note: When you play video on Mac using QuickTime, the easiest way to solve the missing codec error is to convert video to QuickTime compatible format like MOV, QT, M4v, MP4 with HD video converter for Mac.