You can try to use MP4 file fixer to fix it.

Video files can be repaired in most cases. Due to the complexity of video/audio encoding, some situations cannot be repaired. In this case, please use professional video tools to repair it, such as ffmpeg.

CocoCut will buffer all the video data, when buffer finished, Click "Save" below the video preview, The downloaded file will be saved to the default download location of the browser. See detail.

Click "Save buffered parts directly" will save all buffered parts to your computer.

The downloaded files are temporarily stored in the browser's memory, which is automatically emptied when the browser is closed and will not take up any disk or memory space.

Some videos cannot be downloaded directly. The recording mode can record the video while it is playing, and then download it as an MP4 file.

Recording mode uses the resolution when the video is playing, select the resolution to download on the video playback page.

The recording mode will wait for the playback completion signal of the playback page. After receiving the playback completion signal, it will automatically go to the recording completion status. If the video has indeed finished playing, you can directly click the green "Save" button to download the complete video.

CocoCut will try to pull the video data with multiple threads, but the max download speed still depends on your network and the video provider.

CocoCut will directly save the video file to MP4 format, and will not transcode or compress the video. You can re-process the saved MP4 file.

Because the video provider sites do not want their videos to be downloaded, they encrypt the video streams. CocoCut respects the choice of the video provider sites and will not support download such videos.

CocoCut is a universal downloader that can download videos from all web technology-compliant sites, and is not specifically adapted to a single site.

When a site used to be downloadable and then suddenly became unavailable, it is possible that the site modified their video technology.

The reason is the same as above, it is recommended to try to use the MP4 file fixer or FFMPEG, or use 'recording mode'.

It is possible that the video and audio files on the video website are separate. You can go back to the video playback page, click on the CocoCut extension icon in the top right corner of the browser, and see if you can find the corresponding video/audio files in the file list (you can click the 'Play' icon to see what the file contains). After downloading the video/audio files separately, you can use the video-audio merging tool to combine the audio and video files.

It might also be because the video does not conform to web technology standards and uses proprietary or special video technology; in such cases, you can try converting the downloaded video with an MP4 repair tool or a tool like FFMPEG to fix it.

Alternatively, you can try using the 'Recording Mode'.