Is MP4 to MKV conversion lossless?

Yes, when done as a remux: the H.264 or H.265 video and AAC audio are copied into the Matroska container untouched, so picture and sound stay bit-identical. Only the wrapper changes, which is why the conversion finishes in seconds rather than re-encoding for minutes.

What can an MKV hold that my MP4 couldn't?

Soft subtitles in SRT or ASS form, effectively unlimited audio tracks, named chapters, and attachments such as fonts or cover art. MP4 supports some of this in theory, but tooling and player support for those features is far stronger on the MKV side, which is why Plex-style media libraries lean toward it.

Will the MKV still play on my TV or console?

Support is broader than it used to be — recent smart TVs and current consoles generally cope — but older TVs, in-car systems, and many streaming sticks still refuse MKV while playing MP4 happily. Since the conversion is lossless in both directions, keep the MP4 wherever device compatibility is uncertain.

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MKV is a flexible open container that holds multiple video, audio, and subtitle tracks in one file. Converting MP4 to MKV is ideal for movies with several languages or embedded subtitles.

Convert MP4 to MKV – Free Online MP4 to MKV Converter

Why convert MP4 to MKV?

Bundle multiple audio languages and subtitle tracks in one file.
Open container with no licensing restrictions.
Preferred by media servers like Plex and Kodi for rich metadata.

Tip: MKV often just re-wraps the same video stream, so conversion is fast and lossless when codecs are compatible.

How to convert MP4 to MKV

Upload your MP4 file using the area above.
MKV is preselected as the target format.
Click Start and wait for the conversion to finish.
Download your converted MKV file.

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