MP4 to MKV Converter
Moving from MP4 to MKV is often a container change rather than a quality change. When the existing streams are compatible with Matroska, remuxing can avoid re-encoding entirely.
Why this conversion is useful
Moving from MP4 to MKV is often a container change rather than a quality change. When the existing streams are compatible with Matroska, remuxing can avoid re-encoding entirely.
Use MKV when you want a more flexible container for multiple streams, subtitles or a broader set of metadata workflows.
How to do it
- Step 1Open the MP4 file in FastConvert.
- Step 2Choose MKV as the output container.
- Step 3Use automatic/stream-copy behavior when compatible; otherwise choose an explicit video and audio codec.
- Step 4Convert and check the resulting tracks in your target player.
Remux or transcode?
Try to preserve compatible streams first. Remuxing changes the container without re-encoding; transcoding changes the compressed streams and therefore involves quality, bitrate and compute trade-offs.
Frequently asked questions
Will conversion always reduce quality?
No. A compatible remux can preserve the compressed streams exactly. A real transcode introduces a new encode and should be chosen deliberately.
Where do my files go?
The advertised FastConvert workflow processes media locally on Windows rather than uploading it to a conversion server.
Use FastConvert locally. Download for Windows or browse the format guide.