MKV to MP4 Converter
MKV is a container, not a codec, and what is inside it is usually H.264 or H.265 — both of which an MP4 carries happily. When that is the case the streams are copied straight across and the conversion finishes as fast as the file can be read.
What to know about MKV
MKV holds anything, which is the problem
Matroska was designed to carry any codec, any number of tracks, chapters and subtitles. That is why it is the format of choice for archives, and also why phones, editors and TVs so often refuse it — they support the codecs, not the wrapper.
Extra tracks do not survive the move
An MKV with six audio languages and a dozen subtitle tracks cannot be represented in an MP4 the same way. The primary video and audio come across; the rest are left behind, which is usually what you wanted from a file destined for a phone.
When it does have to re-encode
An MKV holding VP9 or AV1 — common for anything saved from the web — cannot be copied into an MP4 that other software will open. That case re-encodes, and the tool tells you before it starts.
What MP4 carries without re-encoding
These are the video codecs a MP4 can hold in a way other software will actually open. If your MKV already contains one of them, the stream is copied across untouched and nothing is re-compressed. Anything else is re-encoded to H.264.
H.264H.265
Need something smaller rather than something different? Compress it to a target size instead — that one aims at a file size you name.
Frequently asked questions
Why will nothing play my MKV?
Because support is for the codecs, not the wrapper. Phones, editors and TVs usually handle the H.264 or H.265 inside perfectly well — they just refuse the Matroska container around it. Repacking as MP4 changes the wrapper and leaves the video alone.
Does it re-encode?
Usually not. If the MKV holds H.264 or H.265, the stream is copied straight into the MP4 and the picture is identical. If it holds VP9 or AV1 — common for anything saved from the web — an MP4 cannot carry it playably, so that case re-encodes and the tool tells you before it starts.
What happens to the other audio tracks and subtitles?
They are not carried over. An MKV rip with six languages and a dozen subtitle tracks cannot be represented in an MP4 the same way, so the primary video and audio come across and the rest are left behind.
Can I get the subtitles out first?
Yes — the subtitle converter reads SRT, VTT and ASS, and the burn-in tool can render them permanently into the picture if the destination will not display a separate track.
Is MKV worse than MP4?
Technically it is the more capable container — it carries more codecs, more tracks and more metadata. It is just far less widely supported, which is the only reason this page exists.