MKV to MP4 — Everything You Need to Know About This Conversion

MKV: The Format Power Users Love and Everyone Else Doesn't Understand

MKV (Matroska Video) is the Swiss Army knife of video containers. It can hold virtually any combination of video, audio, and subtitle tracks — multiple audio languages, forced subtitles, chapter markers, even attached fonts. It's the format of choice for Blu-ray rips, anime with multiple subtitle tracks, and high-quality video archives.

The problem? The rest of the world runs on MP4.

Your smart TV might play it. Your gaming console probably won't. Uploading to social media? Forget it. Embedding on a website? Not a chance. iPhones and iPads give you a blank stare.

Why MKV Exists (And Why It's Actually Great)

MKV was created in 2002 by a small team of developers in Russia, as an open-source alternative to proprietary containers. Its technical capabilities are impressive:

Feature	MKV	MP4
Multiple audio tracks	Unlimited	Limited support
Subtitle tracks	Unlimited (SSA, ASS, SRT)	Limited (text only)
Chapter markers	Full support	Basic support
Attached files	Fonts, cover art, etc.	Limited
HDR10/Dolby Vision	Full support	Full support
Maximum resolution	No limit	No limit
Open standard	Yes (EBML-based)	Yes (ISO standard)
Device compatibility	Limited	Universal

If you've ever downloaded a movie file that lets you switch between English, Japanese, and French audio while displaying custom-styled subtitles — that's MKV doing its thing.

When to Convert (And When Not To)

Convert to MP4 when:

• You need to play the video on an iPhone, iPad, or Apple TV
• You're uploading to YouTube, Instagram, TikTok, or any social platform
• You're embedding video on a website
• You're sharing with someone who isn't tech-savvy
• You're editing in software that doesn't support MKV

Keep MKV when:

• You're archiving video with multiple audio/subtitle tracks
• You're using a media server (Plex, Jellyfin, Kodi) that handles MKV natively
• The file plays fine on your devices and you're not sharing it
• You'd lose subtitle tracks or chapter markers by converting

The Lossless Conversion Trick

Here's something many people don't realize: if your MKV contains H.264 or H.265 video with AAC audio, you can convert to MP4 instantly with zero quality loss. The tool just rewraps the existing streams in an MP4 container — no re-encoding happens.

Smart converters detect this automatically — they'll rewrap without re-encoding whenever possible. A 10 GB file can convert in under 5 seconds this way.

When remuxing doesn't work: If the MKV contains codecs that MP4 doesn't support (like Vorbis audio, FLAC audio, or ASS subtitles), the converter needs to re-encode those specific streams — which takes longer but ensures compatibility.

Online Converters

MyPDF's MKV to MP4 converter handles remuxing when possible, re-encoding only when necessary.

For files over 1 GB (common with MKV), desktop tools are more practical than uploading to a website.

What You Lose in the Conversion

Be aware of what MP4 can't carry over:

MKV Feature	Preserved in MP4?
Video stream	Yes (if H.264/H.265)
Primary audio track	Yes
Additional audio tracks	Usually lost (depends on tool)
SRT subtitles	Can be embedded or lost
ASS/SSA styled subtitles	Lost (convert to SRT first)
Chapter markers	Preserved by some tools
Attached fonts	Lost
Cover art	Lost

If you have an MKV with Japanese audio, English dub, and three subtitle tracks, converting to MP4 typically keeps only the first audio and first subtitle track. HandBrake gives you per-track control to choose which ones to keep.

HandBrake: The Visual Approach

If command lines aren't your thing, HandBrake makes MKV-to-MP4 conversion straightforward:

1. Open Source → Select your MKV
2. Format: MP4
3. Video tab: H.264, Quality RF 20-23
4. Audio tab: Select which tracks to include
5. Subtitles tab: Add subtitle tracks (burn-in or soft subs)
6. Start Encode

HandBrake gives you per-track control that most online converters don't — essential for MKVs with multiple audio/subtitle streams.

File Size Expectations

Scenario	Input (MKV)	Output (MP4)
Remux (same codecs)	8 GB	~8 GB
Re-encode H.265 → H.264	8 GB	~12 GB
Re-encode H.264, lower quality	8 GB	3-5 GB
Re-encode to H.265	8 GB	4-6 GB

Remuxing doesn't change the size. Re-encoding to the same codec at the same quality also stays similar. Size only changes when you change quality settings or switch codecs.

Frequently Asked Questions

Does converting MKV to MP4 reduce quality?

Not if you remux (-c copy). If you re-encode, there's minimal loss at high quality settings. You'd need to compare frames side-by-side to notice.

Why can VLC play MKV but my TV can't?

VLC includes decoders for practically every codec ever made. Your TV's built-in player only supports specific codecs — usually H.264 in MP4. It's a software limitation, not a hardware one.

My MKV has 10-bit HEVC HDR video. Will it survive conversion?

If the converter remuxes (rewraps without re-encoding), yes — the HDR metadata is preserved. If it re-encodes, HDR metadata can be lost unless the tool specifically supports it. For HDR content, look for a converter that offers a "copy streams" or "remux" option.

Can I convert MP4 back to MKV?

Yes, and it's equally instant with the right tool. There's no quality change — just a different container. HandBrake, VLC, and most online converters handle this.

Related Tools

• Convert Video — Convert between all video formats
• Compress Video — Reduce file size after conversion
• Video Trim — Extract specific sections
• MP4 to MP3 — Extract audio from the converted file