What codecs are inside most MKV files?

Common: H.264 (AVC), H.265 (HEVC), AV1 for video; AC-3 (Dolby), DTS, AAC, MP3 for audio. Our converter re-encodes everything to H.264 + AAC. If your MKV uses HEVC or AV1, the conversion takes longer because the video must be fully decoded and re-encoded, rather than just re-muxed.

Will I lose quality converting MKV to MP4?

Some quality reduction occurs because we re-encode with H.264 CRF 23 rather than copying the stream. For typical viewing quality, this is imperceptible. If your MKV is already H.264, a lossless copy would be possible — but browser security restrictions on file access make stream copying less reliable than full re-encoding in this context.

What happens to multiple audio tracks or subtitles in the MKV?

Only the first audio track is included in the output MP4. Subtitles (SRT, ASS, PGS) are not carried over. If you need subtitle support, consider using VLC (free desktop app) which handles MKV subtitles natively without conversion.

My MKV is 500 MB. How long will conversion take?

A 500 MB MKV with H.264 video typically takes 5–20 minutes in the browser, depending on your CPU and the original video resolution. 4K MKVs take longer than 1080p. The page remains fully responsive during conversion — you can switch tabs and come back.

Is there a better option for very large MKV files?

For files over 500 MB, we recommend using HandBrake (free, desktop) or VLC's built-in converter. These use native hardware encoders (GPU acceleration) and are 5–10× faster than browser-based WASM. For quick one-off conversions of files under 200 MB, our browser tool is the easiest option.

Convert MKV to MP4 — Play Anywhere

MKV (Matroska) is a popular container for high-quality video downloads and rips, but it's not supported natively on iPhones, most smart TVs, or in web browsers. This converter re-encodes MKV to H.264 MP4 in your browser using FFmpeg WebAssembly — no file upload, no server, completely private.

Drop files here

or browse to upload

Up to 500.0 MB per file

How to use this tool

Drop your MKV file
Upload the MKV file you want to convert. Common sources: video downloads, media rips, recordings from OBS or Handbrake. Up to 500 MB supported.
Wait for FFmpeg WASM to load
First-time use requires a ~30 MB WebAssembly download. This is cached by your browser, so subsequent conversions start instantly.
Convert to MP4
Click Convert. The video is re-encoded to H.264 + AAC, the most widely supported codec combination. The first audio track is preserved; embedded subtitles are not included in the output.
Download and play
The resulting MP4 plays on iPhone, Android, Apple TV, Roku, Samsung TVs, Chromecast, and all major video players without additional codecs.

Frequently asked questions

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Convert MKV to MP4 — Play Anywhere

How to use this tool

Frequently asked questions

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