Free Video Container Changer Apps for Windows, macOS, and Linux

Free Video Container Changer Apps for Windows, macOS, and LinuxChanging a video’s container (also called remuxing) is often the fastest way to fix playback compatibility, correct metadata, or prepare files for specific devices without degrading quality. Container formats—MP4, MKV, MOV, AVI, WebM, and others—hold video, audio, subtitles, and metadata; moving those streams between containers without re-encoding is called remuxing. This article reviews the best free tools for remuxing across Windows, macOS, and Linux, explains when to remux versus re-encode, and offers step-by-step examples and tips for safe, lossless conversion.

Why change a video container?

• Fix playback issues: Some players or devices only support certain containers (for example, many smart TVs prefer MP4).
• Preserve quality: Remuxing copies existing video and audio streams without re-encoding, so there’s no quality loss.
• Adjust compatibility: Move subtitles, alternate audio tracks, or chapters into a container that supports them (MKV is feature-rich; MP4 is broadly compatible).
• Reduce file size? Not usually—remuxing generally keeps the same size unless you remove streams (e.g., extra audio tracks).

When to remux vs re-encode

• Remux when: your video/audio codecs are already compatible with the target container and you only need a different wrapper, subtitle track changes, or metadata edits.
• Re-encode when: the target device requires a different codec (e.g., H.265 on devices that don’t support it), you need to change resolution/bitrate, or you want to reduce file size.

Recommended Free Tools

Below are reliable, free apps that perform container changes on Windows, macOS, and Linux. Each supports lossless remuxing for many common formats—note platform availability and typical use-cases.

MKVToolNix (GUI + CLI)

• Strengths: Designed for Matroska (MKV) but accepts many input formats; excellent handling of multiple audio tracks, subtitles, and chapter markers.
• Typical workflow:
  1. Open MKVToolNix GUI (mkvmerge GUI).
  2. Add your source file(s).
  3. Uncheck any streams you don’t want to include.
  4. Set output filename and click “Start multiplexing.”
• When to use: You want a feature-rich container (MKV) with multiple subtitle and audio track support and no re-encoding.

FFmpeg (command line)

• Strengths: The swiss-army knife for any media task—remuxing, transcoding, extracting streams, and batch processing.
• Example remux command (copy streams into MP4):

  
  ffmpeg -i input.mkv -c copy -map 0 output.mp4 

• Notes: Use -c copy for lossless remuxing. Some containers require specific adjustments (e.g., MP4 prefers AAC/MP3 audio, H.264/H.265 video compatibility considerations).
• When to use: You need maximum control, automation, or are processing many files.

HandBrake

• Strengths: Friendly UI and device presets make it easy to create MP4 or MKV files tuned for phones, tablets, and web.
• Limitation: Primarily a transcoder — it re-encodes streams by default, which means quality loss (though you can control settings to minimize it).
• When to use: You need to change codecs, resize, or apply filters rather than just a container change.

Avidemux

• Strengths: Simple for quick container swaps; supports “Copy” for both video and audio to avoid re-encoding.
• Typical steps:
  1. Open file.
  2. Set Video Output and Audio Output to “Copy.”
  3. Choose desired Output Format (e.g., MP4 Muxer, MKV Muxer).
  4. Save file.
• When to use: Quick and small tasks when you prefer a GUI and minimal options.

LosslessCut

• Strengths: Focused on lossless cutting and remuxing with a simple timeline UI. Fast because it avoids re-encoding.
• Use cases: Trim out parts, remove unwanted tracks, or change the container while keeping original streams intact.
• Notes: Best for formats that support frame-accurate cutting; relies on FFmpeg internally.

Practical examples

Example 1 — Remux MKV to MP4 with ffmpeg

Command:

ffmpeg -i input.mkv -c copy -map 0 -movflags +faststart output.mp4 

• -c copy: copy streams without re-encoding.
• -map 0: include all streams.
• -movflags +faststart: optimize MP4 for web playback.

Caveat: If the MKV contains codecs unsupported in MP4 (e.g., VORBIS audio), FFmpeg will error or the MP4 may be incompatible; you’d need to re-encode that stream (e.g., -c:a aac).

Example 2 — Extract subtitles and add them to MKV with MKVToolNix

• Load video in MKVToolNix GUI.
• Add external subtitle file (.srt).
• Ensure desired tracks are checked.
• Start muxing.

Tips and troubleshooting

• Check codecs first: inspect a file with ffmpeg -i input.mkv (it will list codecs). If codecs aren’t compatible with the target container, either choose a different container (MKV is more permissive) or re-encode the incompatible streams.
• Subtitles: Soft subtitles stay separate; hardcoding (burning) subtitles requires re-encoding.
• Chapters and metadata: MKV preserves rich metadata; MP4 has limitations—test on the target device.
• Batch tasks: Use ffmpeg scripts or mkvmerge batch commands for multiple files.
• Back up originals before batch processing.

Conclusion

For lossless container changes across Windows, macOS, and Linux, FFmpeg and MKVToolNix are the most powerful and flexible free options; LosslessCut and Avidemux provide quick GUI-driven workflows; HandBrake is ideal when re-encoding or device-specific presets are needed. Choose remuxing when codecs are already compatible to retain full quality and save time.