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Convert MP4 to MKV - Unlock Multiple Audio and Subtitle Tracks

Convert MP4 to MKV - Unlock Multiple Audio and Subtitle Tracks

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Step 2: Choose format
Step 3: Convert files

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Need Multiple Audio Tracks or Subtitle Options in Your Video?

MP4 is the universal video format, but it has limitations. You cannot easily add multiple audio tracks, your subtitle options are restricted, and chapter markers are not well supported. When you need a video with English and Spanish audio, or want to include commentary alongside the main track, MP4 falls short.

MKV (Matroska) is the open-source container format designed for exactly these scenarios. It supports unlimited audio and subtitle tracks, chapter markers like Blu-ray discs, and even lossless FLAC audio. Converting your MP4 to MKV opens up possibilities that the original format simply cannot provide.

How to Convert MP4 to MKV

  1. Upload your MP4 file - Drag and drop or select your video from any device
  2. Confirm MKV output - Your video converts to the flexible Matroska container
  3. Download your MKV file - Get your multi-track capable video instantly

The conversion process preserves your original video and audio quality. Since both MP4 and MKV are container formats, we can often remux the content without re-encoding, maintaining bit-perfect quality in seconds.

Understanding MP4 and MKV Format Differences

Both MP4 and MKV are container formats that wrap video, audio, and metadata. The container does not determine video quality, but it defines what features are available.

  • Audio tracks - MP4 supports only 2 audio tracks, while MKV allows unlimited audio streams in one file
  • Subtitle support - MP4 has basic subtitle embedding, MKV supports advanced formats like ASS/SSA with styling and positioning
  • Codec flexibility - MKV supports virtually any codec including FLAC, DTS, and TrueHD for lossless audio
  • Chapter markers - MKV includes full chapter support similar to DVD and Blu-ray menus
  • Error recovery - MKV can recover from file corruption and continue playback, MP4 files often become completely unplayable
  • File size - With identical codecs and settings, MKV and MP4 produce nearly identical file sizes

In our testing, converting a 1 GB MP4 file to MKV produces a file within 1-2% of the original size when remuxing without re-encoding. The container overhead is negligible.

When MP4 to MKV Conversion Makes Sense

Creating Multi-Language Video Files

If you need a video with multiple audio tracks, such as original English and dubbed Spanish or French, MKV is the only practical choice. Film distributors and media archivists use MKV specifically because it handles multiple languages in a single file without the complexity of separate audio files.

Archiving with Lossless Audio

MP4 does not support FLAC or other lossless audio codecs. If you are archiving concert footage, music videos, or audio-critical content, converting to MKV allows you to preserve audio in FLAC format with zero quality loss. This is essential for audiophiles and professional archives.

Adding Styled Subtitles

MKV supports Advanced SubStation Alpha (ASS/SSA) subtitles with custom fonts, colors, positioning, and karaoke effects. If you need anime fansubs or professionally styled captions, MKV handles these natively while MP4 only supports basic text.

Blu-ray and DVD Ripping

When extracting video from physical media, MKV preserves all audio tracks, subtitle streams, and chapter markers from the original disc. This makes it the standard format for media archiving and personal libraries.

Recording and Streaming

Content creators recording with OBS or similar software often choose MKV because of its corruption resistance. If your recording crashes or power fails, MKV files can often be recovered while MP4 files become completely unusable due to the MOOV atom requirement.

MP4 vs MKV: Which Format to Choose

Both formats excel in different scenarios. Understanding the trade-offs helps you choose correctly.

  • Choose MKV when: You need multiple audio tracks, want lossless FLAC audio, require styled subtitles, are archiving Blu-ray content, or want corruption-resistant recordings
  • Keep MP4 when: Sharing on social media, streaming to mobile devices, uploading to YouTube or Vimeo, or needing maximum device compatibility
  • Consider the trade-off: MKV plays on VLC, Plex, Kodi, and most desktop players, but may not work natively on iPhones, some smart TVs, or older devices without transcoding

For everyday sharing and streaming, MP4 remains the safer choice. Convert to MKV when you specifically need its advanced container features.

Playback Compatibility for MKV Files

While not as universal as MP4, MKV enjoys broad support on modern platforms and media centers.

  • Desktop players - VLC, PotPlayer, MPC-HC, and mpv play all MKV files natively
  • Media servers - Plex, Jellyfin, and Kodi handle MKV as their preferred format
  • Smart TVs - Most Samsung, LG, and Sony smart TVs support MKV playback
  • Streaming devices - Roku, Fire TV, and Chromecast with Google TV support MKV natively
  • Mobile - Android plays MKV in most video apps, iOS requires third-party players like VLC or Infuse

For home theater setups and personal media libraries, MKV compatibility is rarely an issue. Problems mainly occur with web sharing or iOS devices.

Batch Convert Multiple MP4 Files

Building a media library or converting an entire season of videos? Upload multiple MP4 files at once and download them all as MKV. Batch conversion is essential for archivists converting large collections, content creators standardizing on MKV for their workflow, or anyone migrating their video library to a more flexible format.

Works on Any Device

Our browser-based converter runs entirely in your web browser. No software to install, no plugins required, and no account needed to start converting.

  • Windows, Mac, Linux, ChromeOS
  • Chrome, Firefox, Safari, Edge
  • iPhone, iPad, Android tablets and phones

Convert your MP4 files from any device, then transfer the MKV output to your preferred media player or server.

Pro Tip

When archiving video, use MKV with the original video codec but upgrade audio to FLAC. This preserves visual quality while ensuring audio fidelity that AAC or MP3 cannot match. The file size increase is modest compared to the quality improvement.

Common Mistake

Users convert MP4 to MKV expecting it to play on iPhones or upload to YouTube. MKV is not supported on iOS natively and most streaming platforms reject it. Convert only when you need MKV-specific features like multiple audio tracks or lossless audio.

Best For

Perfect for building Plex or Jellyfin media libraries, archiving Blu-ray content with all audio tracks and subtitles, recording with OBS for crash recovery, and storing videos with multiple language options in a single file.

Not Recommended

Not ideal for sharing on social media, uploading to YouTube or Vimeo, sending to iPhone users, or maximum device compatibility. Keep MP4 for distribution and use MKV for archiving and personal media servers.

Frequently Asked Questions

No quality loss when remuxing. Since both are container formats, we can transfer the video and audio streams directly without re-encoding. The conversion is essentially repackaging the same content. Only transcoding between different codecs causes quality loss.

MP4 officially supports only 2 audio tracks, while MKV allows unlimited audio streams. This makes MKV ideal for movies with multiple language options, director commentary, audio descriptions, and other supplementary audio content in a single file.

Yes, MKV is one of the few container formats that supports FLAC audio. This is perfect for archiving concert footage, music videos, or any content where audio quality is paramount. MP4 does not support FLAC, making MKV the only practical option for lossless audio.

Most modern smart TVs from Samsung, LG, Sony, and Vizio support MKV playback natively. Older models may require a media server like Plex to transcode on the fly. Check your TV specifications for MKV and specific codec support like H.264 or HEVC.

YouTube, Vimeo, and social media platforms standardized on MP4 because of its universal device compatibility and DRM support. MKV is an open format without DRM, making it unsuitable for protected content distribution. For uploading to these platforms, keep your files in MP4.

Embedded MP4 subtitles transfer directly to MKV. Additionally, MKV supports advanced subtitle formats like ASS/SSA with custom styling, fonts, and positioning that MP4 cannot handle. You can add multiple subtitle tracks in different languages after conversion.

With identical video and audio content, MKV and MP4 files are nearly the same size. The container overhead is only a few kilobytes. MKV files may appear larger when they contain additional audio tracks or subtitle streams that the original MP4 lacked.

iOS does not support MKV natively in the Photos or Videos app. However, third-party players like VLC, Infuse, and nPlayer handle MKV files perfectly. If you use Plex or Jellyfin, their iOS apps will play or transcode MKV content seamlessly.

MKV has built-in error recovery that allows playback of corrupted files. If OBS crashes during recording, an MKV file can often be recovered while an MP4 file becomes completely unplayable due to the missing MOOV atom. Many creators record in MKV then convert to MP4 for distribution.

Remuxing without re-encoding takes seconds regardless of file size since we are just repackaging existing streams. A 5 GB movie file converts in under 30 seconds. If transcoding is required for codec changes, conversion time depends on file length and resolution.

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