18 Best MP4 to MKV Converters in 2026 (Free and Paid)

MP4 to MKV is the conversion that home media libraries, anime collections, and Plex/Jellyfin servers rely on. MKV (Matroska) is the open-source video container that handles everything MP4 cannot: multiple audio tracks, multiple subtitle tracks (including SRT, ASS, and PGS forced subs), chapter markers, embedded fonts, and attached files. Most importantly, MP4 → MKV is usually a remux — a container change with no re-encoding, so it is instant and lossless. This guide compares 18 MP4 to MKV converters in 2026.

How to Convert is listed first because it is made by the same indie developer who writes this blog. The remux vs re-encode distinction is the most important thing to know about MP4 → MKV — the next section covers it.

Remux vs Re-encode

• Remux — copy the existing video and audio streams into the MKV container as-is. No re-encoding. Instant (seconds for a 4 GB file). Bit-identical. The default for any sensible MP4 → MKV conversion.
• Re-encode — decode the video and audio, encode them again with a new codec. Takes time. Adds a small quality loss. Only useful if you need to change the codec (e.g., to fit a target device's decoder limits).

Good tools default to remux. Bad tools always re-encode and burn CPU time for no gain. The CLI for a clean remux:

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

The -c copy tells FFmpeg to copy streams without re-encoding.

Quick Picks for MP4 → MKV

• Best CLI: FFmpeg with -c copy.
• Best GUI for media library work: MKVToolNix.
• Best for editing during conversion: HandBrake (re-encode).
• One-shot: How to Convert.

One-shot: MP4 to MKV converter.

1. How to Convert

Drop MP4s in, pick MKV, hit convert. Defaults to remux (no re-encode), so a 4 GB file finishes in seconds with no quality loss.

Pricing

• One-time license; free trial.

2. MKVToolNix — best dedicated MKV tool

MKVToolNix is the Matroska reference toolkit. Its mkvmerge GUI handles MP4 → MKV remux with full control over which tracks to include, chapter markers, attached subtitles, and global tags. Indispensable for media library work.

CLI:

mkvmerge -o output.mkv input.mp4

With an external SRT subtitle:

mkvmerge -o output.mkv input.mp4 --language 0:eng subtitles.srt

Pricing

• Free, open source.

3. FFmpeg

Remux (no re-encode, instant):

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

With explicit subtitle track preservation:

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

Batch:

for f in *.mp4; do ffmpeg -i "$f" -c copy -map 0 "${f%.mp4}.mkv"; done

Pricing

• Free, open source.

4. HandBrake

HandBrake re-encodes by default, so MP4 → MKV through HandBrake is slower than a remux. Useful if you also want to change the codec (e.g., re-encode H.264 to H.265 to save space).

Pricing

• Free, open source.

5. Shutter Encoder

Free FFmpeg GUI with explicit remux options.

Pricing

• Free.

6. VLC

Media → Convert / Save → output MKV. Limited remux support; usually re-encodes.

Pricing

• Free, open source.

7. mkvtoolnix-gui

The official MKVToolNix graphical front-end. Drag MP4 in, choose tracks to include, save MKV. Best for adding external subtitles or chapter files during the conversion.

Pricing

• Free, open source.

8. Permute (Mac)

Mac-native media converter with MKV output.

Pricing

• One-time purchase.

9. Any Video Converter

Consumer converter with MKV output.

Pricing

• Freemium.

10. Wondershare UniConverter

Full media suite with MKV remux option.

Pricing

• Paid.

11. Movavi Video Converter

Beginner-friendly paid converter.

Pricing

• Paid.

12. Adapter

Free Mac and Windows media converter.

Pricing

• Free.

13. tsMuxeR

Older dedicated muxer for video container conversion. Useful for Blu-ray-source workflows.

Pricing

• Free.

14. DaVinci Resolve

MKV export via Deliver page. Always re-encodes; not the right pick for pure remux.

Pricing

• Free Studio edition; paid Studio.

15. CloudConvert

Web converter with MKV output.

Pricing

• Free tier; paid above.

16. Convertio

Web MP4 → MKV.

Pricing

• Free with caps; paid above.

17. Online-Convert

Web converter with detailed options.

Pricing

• Free with limits; paid above.

18. FreeConvert

Web converter with codec choice.

Pricing

• Free with caps; paid above.

How to Choose

• Quick remux: FFmpeg -c copy or How to Convert.
• Adding subtitles or chapters: MKVToolNix.
• Plex / Jellyfin library work: MKVToolNix or FFmpeg.
• Re-encode to a different codec: HandBrake.
• One-off: any web tool.

Final Thoughts

MP4 → MKV should almost always be a remux — instant, lossless, no re-encoding. FFmpeg with -c copy is the gold standard; MKVToolNix is the friendly GUI; How to Convert handles the remux default automatically. Avoid tools that re-encode by default — they waste hours of CPU time and add quality loss for no benefit.