How to Join Multiple MKV Files Together

Merging multiple MKV (Matroska) video files into a single, seamless file is a highly straightforward process that can be completed in just a few minutes. This article explains how to easily join MKV files without losing any video or audio quality, highlights the best free tools for the task, and provides step-by-step instructions on how to combine your video files on Windows, macOS, and Linux.

Can MKV Files Be Merged Without Quality Loss?

Yes. Because MKV is a container format, you can merge multiple MKV files together without re-encoding the video or audio. This process is called “multiplexing” (or muxing). Since the video is not being compressed again, the merging process is nearly instantaneous and results in zero quality loss.

However, for a lossless merge to work seamlessly, the input MKV files should ideally share the same properties, including: * Video resolution (e.g., 1080p, 4K) * Frame rate (e.g., 24fps, 30fps, 60fps) * Video and audio codecs (e.g., H.264/AAC, H.265/HEVC)

If the files have different resolutions or codecs, you will need to re-encode them to a matching format before joining, or use a video converter that handles the transition.

The Best Tool for the Job: MKVToolNix

The absolute best and most reliable tool for merging MKV files is MKVToolNix. It is a free, open-source suite of tools designed specifically for the Matroska format. It is available for Windows, macOS, and Linux.

Step-by-Step Guide to Merging MKV Files with MKVToolNix

  1. Download and Install: Download MKVToolNix from its official website and install it on your computer. Open the application named MKVToolNix GUI.
  2. Add the First File: Drag and drop your first MKV file into the “Source files” window, or right-click within the window and select “Add files.”
  3. Append the Remaining Files: To ensure the videos play one after another, do not just drag the other files in normally. Instead, right-click your first file in the source list and select “Append files”. Select the second MKV file. Repeat this step for any subsequent files in the exact order you want them to play.
  4. Set Output Destination: At the bottom of the window, choose your desired “Destination file” path and name for the merged video.
  5. Start the Merge: Click the “Start multiplexing” button at the bottom of the interface. The tool will join the files within seconds.

Alternative Method: Using FFmpeg (Command Line)

For advanced users who prefer command-line tools, FFmpeg is an excellent, lightweight alternative that requires no graphical interface.

To join MKV files using FFmpeg without re-encoding, follow these steps:

  1. Create a text file named inputs.txt in the same folder as your MKV files.

  2. List the files you want to merge in the text file using the following format:

    file 'video1.mkv'
file 'video2.mkv'
file 'video3.mkv'

  3. Open your command prompt or terminal in that folder and run the following command:

    ffmpeg -f concat -safe 0 -i inputs.txt -c copy output.mkv

FFmpeg will quickly concatenate the files and output a single, high-quality output.mkv file.