How to Convert MKV to MP4: Complete Guide
MKV (Matroska Video) is a versatile open container that can hold virtually any combination of video, audio, and subtitle tracks. While MKV is the preferred format for high-quality video archiving and media enthusiasts, it lacks universal device support. Many smart TVs, game consoles, and mobile devices cannot play MKV files natively. Converting MKV to MP4 solves these compatibility issues, and in many cases can be done through remuxing with zero quality loss.
Try It Now — Free →MKV vs MP4: Format Comparison
Both are modern container formats, but they serve different purposes.
| Feature | MKV | MP4 |
|---|---|---|
| Multiple Audio Tracks | Unlimited tracks | Multiple tracks (limited support) |
| Subtitle Formats | ASS/SSA, SRT, PGS, VobSub | TX3G, SRT (limited) |
| Chapter Support | Full XML-based chapters | Simple chapter markers |
| Attachment Support | Fonts, cover art, any file | Limited |
| Video Codecs | Any codec (H.264, H.265, VP9, AV1, etc.) | H.264, H.265, AV1 |
| Device Compatibility | Limited (PC, some smart TVs) | Universal |
| Streaming Support | Limited | Full (HLS, DASH) |
| File Size | Same as MP4 (container overhead is minimal) | Same as MKV |
How to Convert MKV to MP4 Step by Step
- 1
Identify the MKV Codecs
Check what video and audio codecs your MKV uses. If it contains H.264 or H.265 video with AAC audio, you can remux (repackage) without re-encoding for zero quality loss and instant conversion.
- 2
Upload Your MKV File
Select the MKV file for conversion. MKV files can be large, especially those containing multiple audio tracks and subtitle streams. A typical 1080p movie in MKV is 4-8 GB.
- 3
Choose Conversion Method
If remuxing is available and your codecs are MP4-compatible, choose remux for lossless conversion. Otherwise, select re-encode with H.264 and AAC.
- 4
Handle Multiple Tracks
MKV files often contain multiple audio tracks (different languages) and subtitle tracks. Select which tracks to include in the MP4 output, as MP4 has more limited multi-track support.
- 5
Convert and Verify
Start the conversion and verify the output. Check that the correct audio track is selected, subtitles display properly, and chapter markers are preserved if applicable.
Recommended MKV to MP4 Settings
The ideal settings depend on whether remuxing or re-encoding is required.
If the MKV contains H.264/H.265 video and AAC audio, remuxing preserves perfect quality in seconds. This is always the preferred method.
If re-encoding is required (e.g., VP9 or unusual codec in MKV), use H.264 with CRF 18-20. If the source is already H.264/H.265, copy the stream directly.
MKV files may contain 2-8 audio tracks in different languages. Select the track you need, as including all tracks can cause compatibility issues on some devices.
If the MKV audio is AC3/DTS (common in movie files), it must be re-encoded to AAC for MP4 compatibility. Use 256 kbps for surround sound down-mixed to stereo.
MKV ASS/SSA subtitles with styling are not fully supported in MP4. Convert to SRT for basic text, or burn subtitles into the video for styled/positioned subtitles.
MP4 supports basic chapter markers. Complex MKV chapters with nested entries may be simplified during conversion.
Common MKV to MP4 Conversion Issues
Audio is in DTS/AC3 and won't play on mobile devices
DTS and AC3 audio are not supported in the MP4 container on most mobile devices. Re-encode the audio track to AAC-LC at 192-256 kbps during conversion.
Styled subtitles (ASS/SSA) lost formatting
MP4 does not support ASS/SSA subtitle formatting (colors, positioning, animations). Either burn the subtitles into the video or accept simplified SRT text subtitles.
Only one audio track in the output
Some converters only process the first audio track by default. Explicitly select multiple audio tracks if your target player supports multi-track MP4 playback.
Output file plays with wrong audio language
The converter may have selected the wrong default audio track. Specify the desired audio track by its index or language tag during conversion.
Conversion fails for MKV with HEVC + 10-bit color
Some converters struggle with 10-bit HEVC (common in high-quality anime and HDR content). Use a converter that supports 10-bit color depth, or re-encode to 8-bit H.264 if target devices lack 10-bit support.
Chapter markers missing in the MP4 output
Not all converters preserve chapter information. Use a tool that explicitly supports chapter copying from MKV to MP4, or add chapters manually after conversion.
When to Convert MKV to MP4
Converting MKV to MP4 is recommended in these situations:
- Your smart TV, game console, or media player does not support MKV playback natively
- You need to upload the video to a social media platform or video hosting service that only accepts MP4
- You want to stream the video from a web server, as MP4 has better progressive download and adaptive streaming support
- You need to edit the video in software that has limited or no MKV import support
- You are sharing the video with someone who uses a device or player that cannot handle MKV files
- You want to reduce the number of audio/subtitle tracks to simplify the file for a specific audience
Frequently Asked Questions
Can I convert MKV to MP4 without losing quality?
Yes, if the MKV contains H.264/H.265 video and AAC audio. Remuxing changes only the container format without touching the video/audio streams, resulting in zero quality loss.
Why are MKV files so large?
MKV files themselves are not inherently large. They often seem large because they commonly contain high-bitrate video, multiple audio tracks (different languages, commentary), and multiple subtitle streams, all in a single file.
Will I lose subtitles when converting MKV to MP4?
Basic SRT subtitles can be preserved in MP4. However, styled ASS/SSA subtitles (with fonts, colors, positioning) will lose their formatting because MP4 does not support these features. Consider burning them into the video to preserve styling.
Can I keep multiple audio tracks in MP4?
MP4 technically supports multiple audio tracks, but device and player support varies. Most mobile devices and basic players only recognize the first audio track. For guaranteed multi-language support, keep separate MP4 files or use a player like VLC.
What happens to DTS audio during conversion?
DTS audio must be re-encoded to AAC for MP4 compatibility, which means converting from lossy to lossy. Use 256 kbps AAC for the best quality when downmixing 5.1 surround to stereo.
Is MKV or MP4 better for quality?
Neither container affects video quality. Both MKV and MP4 can hold the same codecs at the same bitrates. MKV is more flexible (supports more codecs and features), while MP4 is more compatible.
How long does MKV to MP4 conversion take?
Remuxing takes only seconds regardless of file size. If re-encoding is required (codec change), expect 5-15 minutes per hour of 1080p video on modern hardware.
Can I convert MKV with HDR to MP4?
Yes, but HDR metadata preservation depends on the converter. For HEVC HDR10 content, remuxing to MP4 preserves HDR. For Dolby Vision MKV files, conversion is more complex and may lose DV metadata.
Converting MKV to MP4 unlocks universal device compatibility while preserving video quality through remuxing when possible. Focus on audio codec compatibility (convert DTS/AC3 to AAC), handle subtitle format limitations, and always verify multi-track and chapter preservation in the output. For most users, remuxing provides instant, lossless conversion that solves all MKV playback issues.
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