MKV to MP4 Converter - Convert MKV to MP4 Online Free, Lossless

How to convert MKV to MP4

Add your MKV videos. Drop up to 20 MKV files into the box, or browse for them. Each one can be up to 200 MB.
Keep Match source for a lossless remux. With Match source and no trimming or resizing, H.264 + AAC MKVs are copied into MP4 without re-encoding.
Resize or trim if you need to. Pick 720p for a smaller file, or set the start and end under the player. This re-encodes the video.
Convert and download. Press Convert. One or two files download directly, more than two come as a ZIP with a README.

Need the soundtrack on its own? MP4 to MP3 takes MKV files too.

What is an MKV file?

MKV (Matroska) is a container, a box that can hold almost anything.

One MKV can carry several audio languages, subtitles, chapters and nearly any codec.

That flexibility is why downloads, OBS recordings and Blu-ray rips love it - and why iPhones, many smart TVs, PowerPoint and some editors do not. MP4 is the format they all expect.

Lossless remux or re-encode?

Many MKVs already hold H.264 video and AAC sound - the exact codecs MP4 uses. Then the page performs a remux: the streams are copied into an MP4 box as they are.

A remux takes seconds, the quality is identical and the file size stays about the same. The result card says "lossless remux" when that happened.

H.264 with AC3, DTS or FLAC sound - the video is copied, only the sound is converted to AAC.
HEVC, VP9, MPEG-4 or others - the video is re-encoded to H.264 at CRF 20, visually lossless.
Trim, resize or a lower frame rate - always re-encodes, because the picture changes.

Audio tracks and subtitles

To be honest about it: the MP4 gets one video and one audio track - the first ones stored in the MKV.

Extra audio languages, subtitle tracks and attachments such as fonts are left out. If the first audio track is not the language you want, set it as the first track with a desktop tool like MKVToolNix before converting.

Subtitles are not burned into the picture either. Keep the MKV if you need them, or use a player that loads a separate .srt file.

MKV vs MP4

	MKV	MP4
Made by	Matroska (open source)	MPEG (ISO standard)
Codecs	Almost any	H.264, HEVC, AV1 + AAC
Audio tracks	Many, with languages	Usually one
Subtitles	Many styled tracks	Basic, rarely supported
Plays on	VLC, Plex, Kodi, PCs	Everything, including iPhone and TVs
Web upload	Often rejected	Accepted everywhere

Have older clips too? AVI to MP4 converts DivX and Xvid files the same way.

Tips

OBS recording? OBS saves MKV so a crash does not ruin the file. Converting with Match source is usually a lossless remux.
Video too big to share? Pick Web 720p - often 3-5x smaller and still sharp on a phone.
10-bit HEVC MKV? It becomes 8-bit H.264, which every TV and phone can play.
Want a looping clip? Convert, then use MP4 to GIF.

Your video is converted on our server with FFmpeg. The upload is deleted right after converting and the MP4 once you download it.

Frequently Asked Questions

Drop your MKV into the box, keep the Match source preset and press Convert.

One or two files download directly, more than two come as a ZIP.

Not when the MKV holds H.264 video and AAC sound - then it is remuxed, which copies the streams without touching them. Other codecs are re-encoded at CRF 20, which is visually lossless.

A remux moves the video and sound into a new container without re-encoding them. It is lossless, takes seconds and keeps the file size about the same.

No. The MP4 gets the first video track and the first audio track of the MKV. Extra languages, subtitle tracks and attached fonts are left out, and subtitles are not burned into the picture.

Yes. HEVC MKVs, including 10-bit ones, are converted to 8-bit H.264 MP4 that plays on older TVs, Windows and every browser.

Many TVs, iPhones and editors do not open the MKV container, even when the video inside is fine. MP4 is supported everywhere.

Up to 200 MB per video and 20 videos per batch. For full-length movies, use a desktop tool such as HandBrake or MKVToolNix.

Yes, it is free with no account. Your video travels to our server over HTTPS, is deleted as soon as the MP4 is made, and the MP4 is deleted once you download it.