Convert MKV to MP4
Turn MKV files into universally playable MP4s — often instantly, always privately on your device.
MKV (Matroska) is a great container for storing video — it holds almost any codec, multiple audio tracks, and soft subtitles — but plenty of players, editors, and websites refuse to open it. MP4 is the safe target: it plays on every phone, browser, TV, and editing app.
The good news is that most MKV files already contain MP4-compatible video (H.264 or H.265) — so the default Fast remux mode simply moves the streams into an MP4 container without re-encoding. That takes seconds even for gigabyte files and loses zero quality. If your MKV uses an incompatible codec and the remux fails, switch to Re-encode mode, which converts the video to H.264 that plays anywhere.
How to mkv to mp4 online
- 1Drop your .mkv file into the box above — nothing is uploaded.
- 2Keep Fast remux selected; it works for most MKV files and finishes in seconds.
- 3Click Convert, and if the fast mode errors, re-run in Re-encode mode.
- 4Download your MP4.
Frequently asked questions
Will converting MKV to MP4 lose quality?
Not in Fast remux mode — the video and audio streams are copied bit-for-bit into the new container, so quality is identical to the source. Re-encode mode re-compresses at high quality (CRF 20), where any difference is essentially invisible.
Why did Fast remux fail on my file?
MKV can contain codecs the MP4 container doesn't accept — like Vorbis audio or older DivX video. When that happens, switch to Re-encode mode, which converts the streams to H.264 and AAC that MP4 supports.
What happens to subtitles in my MKV?
Soft subtitle tracks are dropped during conversion — MP4 subtitle support is inconsistent across players. If you need subtitles preserved, keep the original MKV alongside your converted MP4.
Is there a file size limit?
No hard limit. Because remuxing doesn't decode the video, even multi-gigabyte MKVs convert in seconds — the practical ceiling is your device's memory, roughly 2 GB in most browsers.
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