MKV to MP4 Converter

MKV to MP4 — the fastest video "conversion" you'll ever do

MKV files containing H.264 or H.265 video don't need to be re-encoded to become MP4s. The video data is copied straight into the new container without touching a single frame. This is called remuxing, and it runs at storage speed — a 10 GB movie that would take 20 minutes to transcode remuxes in about 30 seconds.

The quality is byte-for-byte identical to the original. It's not "converted" in any meaningful sense — it's the same data in a different envelope.

Why iPhones and iPads can't play MKV

Apple chose not to implement Matroska (MKV) container support in iOS and macOS's built-in video player. The irony is that the video codec inside the MKV file (almost always H.264 or H.265) is hardware-accelerated on every Apple device. Your iPhone can decode that video perfectly — it just won't open the MKV wrapper. Converting to MP4 puts the identical video in a container Apple recognises, and it plays instantly.

Why the conversion is so much faster than other video jobs

Most "video conversion" tools you've used are actually re-encoding: decoding every frame and running it through the encoder again. That's computationally expensive. Remuxing does none of that — it reads the compressed video stream as raw bytes and writes them to a new file. CPU usage stays near zero. Time is determined entirely by how fast your storage can read and write, not by processing power.

What happens to each track type during conversion

H.264 video

Remuxed directly. Zero quality loss. This is the vast majority of MKV files downloaded from the internet or recorded by OBS.

H.265 / HEVC video

Also remuxed directly. H.265 is fully supported inside MP4 containers.

AAC or MP3 audio

Remuxed directly. Both work natively in MP4.

AC-3 / DTS audio (surround sound)

Usually remuxed. Some devices that play MP4 don't support AC-3, so you may want to convert to AAC if you need maximum compatibility on phones or browsers.

Subtitles

SRT text subtitles convert to MP4's subtitle format. Complex styled subtitles (ASS/SSA) and bitmap subtitles (PGS from Blu-ray rips) may need to be burned in or dropped.

OBS users — why OBS defaults to MKV and when to convert

OBS records in MKV by default because the format is crash-resistant: if OBS crashes mid-recording, everything recorded up to that point is still playable. MP4 files that are interrupted during writing become completely unreadable. Once your recording session finishes cleanly, remuxing to MP4 is a good habit — it makes the file easier to import into Premiere, DaVinci Resolve, or any other editor.