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How to Convert MKV to MP4 Using FFmpeg for Free?

“Can I use FFmpeg for MKV to MP4 file conversion? Unfortunately, my office computer doesn’t seem to read the MKV video, and I am behind my project deadline.”

Standard users are generally unable to convert videos from MKV to MP4 containers. The MKV file format is incompatible, and this can cause a world of trouble, especially if it’s a video you have invested money in recording or someone else made for you.

We will highlight using open-source FFmpeg so that you can instantly perform the said file conversion. Moreover, we will also share other techniques that are better alternatives to FFmpeg. So keep reading!

Part 1. Steps with Pictures to Convert MKV to MP4 in FFmpeg

The best way to convert MKV to MP4 is an easy one: copy the existing video, audio, and subtitle streams and place them all into a new container, which will serve as the new save point.

This avoids any encoding task altogether, which means you’ll have no issue with quality, and it’s also relatively quick because it won’t require much CPU power - only disk write speed.

Here are the steps to convert MKV to MP4 with FFmpeg

  • Access FFmpeg through the Command Prompt utility.
  • Enter the following command to convert the MKV video:
    ffmpeg -i video.mkv -c copy video.mp4

For batch conversion, place all the MKV videos into a single directory, and enter the command stated below, which will turn the files into MP4 without changing the file names:

for /R %f IN (*.mkv) DO ffmpeg -i "%f" -c copy "%~nf.mp4"

Part 2. Best FFmpeg Alternative to Batch Change MKV to MP4 Easily

Converting videos from MKV to MP4 using Wondershare UniConverter is an excellent choice for those who prefer drag-and-drop rather than using command lines. The latter method is effective, but it can be quite daunting for newbies in this field.

The UniConverter offers users a familiar experience that includes drop-down menus and basic options for converting MKV video files to MP4 instead of complicated buttons and features expected of advanced tools.

This software is available on both Windows and Mac computers, so if you’re switching between multiple systems or if you need to move your workspace around, then this app provides an excellent solution. In addition, it offers 90x conversion speed and is compatible with 1000+ file formats.

Check out the list below to know what more the Wondershare UniConverter has to offer:

wondershare uniconverter 13

Wondershare UniConverter — All-in-one Video Toolbox for Windows and Mac.

safe mov video converter free download Security Verified. 3,591,664 people have downloaded it.

Video Compressor – To reduce the original size of videos suitable for smaller devices

Video Converter – To convert videos/images in 1000+ formats at 90X faster speed.

DVD Burner – To burn videos to DVDs with awesome templates.

Auto Reframe – To instantly resize videos for YouTube/Instagram/TikTok, etc

Background Remover – To erase the video background quickly in batch

Please follow the steps as follows to perform batch conversion of MKV to MP4:

Step 1 Open the Wondershare UniConverter

Access the software on your desktop, and click the Converter button. Now, tap Add+ to import multiple MKV files to the UniConverter.

Open the Wondershare UniConverter

Step 2 Customize the MKV Video Settings

Click the Settings tab, available on the interface’s bottom half, to change the Encoder, Quality, Bitrate, and Frame Rate settings. Also, select the Output Format section to pick MP4 as the new file type.

Customize the MKV Video Settings

Step 3 Convert MKV to MP4

Once everything is set and done, click Start All on the bottom-right corner for batch conversion.

Convert MKV to MP4

Part 3. Other 6 Free Ways to Convert MKV to MP4 Online/Offline

Besides Wondershare UniConverter, if you are looking for other alternatives to convert MKV to MP4, then this section is just for you. Here, we have listed the 6 different online and offline free file converters:

3 Online Ways to change MKV to MP4:

First, we will discuss the online converters that will allow you to perform file conversion without installing any software:

1. CloudConvert

CloudConvert can be used by anyone looking for an easy way to convert MKV files to MP4 on the go. This tool simplifies your file conversion process, so you don’t have to waste time trying to convert your personal media collection using complicated and time-consuming software.


Maintains file quality

It also supports uploading files from Google Drive, Dropbox, OneDrive, and URL


Compatible with only MP4, WebM, AVI, MOV, and WMV formats.

2. FreeConvert

It is a safe and handy online tool to complete MKV file conversion using any modern browser. Besides adding the videos from your computer storage, you can also add media from cloud services, such as Google Drive and Dropbox.


It can convert 1GB files for free

256-bit SSL encryption


Too many ads

Slow processing

Non-existent customer support

3 Free Ways to transform MKV to MP4 Offline:

Check out some handy free-to-use offline file converters here:

1. VLC

VLC is not only a familiar media player but also a useful platform to convert MKVs to MP4 videos without any hassle. You can easily access VLC on your Windows and macOS desktop.




Not a full-time file converter

Limited format support

Complicated process to convert files

2. Freemake Video Converter

If you want to convert the MKV file to play it on any specific device, then the Freemake tool is an excellent choice. It supports every format in the book and can also edit media files.


The tool supports 500+ file formats



Only available on Windows

3. Wondershare Free Video Converter

Whether you want to convert MKV files to MP4, edit them, or manage their metadata for free, then this tool is a recommended choice for you. It supports 1000+ file types and offers batch conversion on both Windows and macOS.


Free and Reliable

Fast processing


Limited editing features

Part 4. FAQs about Using FFmpeg to Convert MKV toMP4

1. Why is there no audio after converting MKV to MP4 using FFmpeg?

If the audio format is not in MP3 or AAC format, you could be facing no sound issue after converting MKV to MP4 with FFmpeg. However, in that case, we recommend converting the audio to MP3 or AAC before changing the video format.

2. Why does FFmpeg lose video subtitles after converting MKV to MP4?

As a container format, most MKV files keep the subtitle files inside them. Therefore, before converting MKV to MP4, you should save the exact name of the subtitle as the video file. If you do not perform the said activity, the subtitle may get lost.


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