MP4 to MKV Converter
Convert MP4 videos to MKV instantly by copying the streams, with no quality loss. Your files are never uploaded to our servers. ToolkitPoint processes them on your own computer, so confidential documents stay with you.
Processed in your browser. Your files are not uploaded.
How to use MP4 to MKV Converter
- The output container is preset to MKV.
- Choose one or more MP4 files.
- Leave the fast stream copy on to keep the original quality.
- Convert and download the .mkv files.
What MP4 to MKV Converter does
Convert MP4 videos to MKV instantly by copying the streams, with no quality loss.
Most media work stays in browser memory. Heavy converters lazy-load a local WebAssembly engine only after processing starts. For MP4 to MKV Converter, the operation is specifically to convert MP4 videos to MKV instantly by copying the streams, with no quality loss.
Worked example
A 200 MB movie-clip.mp4 remuxes to movie-clip.mkv in seconds, with the same video, audio and subtitle tracks and no quality change.
When MP4 to MKV Converter is the right tool
- Using media servers and players that prefer Matroska files.
- Keeping every audio and subtitle track together in one container.
How to verify the result
Play the beginning and end of the output, confirm duration and format, and check lip-sync or audio quality where relevant. The final MP4 to MKV Converter output should visibly match this goal: Convert MP4 videos to MKV instantly by copying the streams, with no quality loss.
Important limitations
Large media jobs can be slow or run out of browser memory. Keep the tab open and use desktop software for very large or production-critical files. This matters here because MP4 to MKV Converter is designed to convert MP4 videos to MKV instantly by copying the streams, with no quality loss, not to repair unrelated source problems.
A free MP4 to MKV Converter alternative
People looking for MP4 to MKV Converter often compare products such as CapCut, Kapwing, VEED. ToolkitPoint is not affiliated with those services. This page keeps convert mp4 videos to mkv instantly by copying the streams, with no quality loss free and available without an account; features, limits, and policies on other products can change, so compare their current product pages before choosing.
Last updated: September 28, 2026
Frequently asked questions
Is MP4 to MKV lossless?
Yes, with stream copy. The tracks are moved into the MKV container unchanged, so quality and size stay the same.
Why is it so fast?
Nothing is re-encoded; only the container around the streams changes.
Are all tracks kept?
Yes. When everything can be copied, all video, audio and subtitle streams are carried over.
What is the size limit?
Files up to 250 MB are supported, because the browser holds them in memory.
Is it private?
Yes. The file never leaves your device.