Convert MKV to MP4
Turn MKV (Matroska) video into MP4 that plays on phones, TVs and Apple devices, without uploading your file to anyone.
🔒 Your file is processed on your device and never uploaded.
MKV, the Matroska container, is popular for downloaded and high-quality video because it can hold almost anything: multiple audio tracks, subtitles and modern codecs in one file. The catch is playback. Plenty of phones, smart TVs and especially Apple devices will not open an MKV, and most upload forms reject it. Converting MKV to MP4 re-encodes the video and audio into the container everything supports.
It all runs inside your browser: the file is converted on your device and never reaches a server, which matters because MKV files are often large and personal. In March 2025 the FBI's Denver office warned it was increasingly seeing criminals use free online file converters to spread malware, including ransomware, so converting locally sidesteps that risk.
MKV can hold many different codecs, so this reads it with a built-in compatibility engine when the browser cannot decode the video directly, then writes a standard H.264 MP4 that plays anywhere. You can lower the resolution or pick a quality preset to bring the file size down.
How to convert MKV to MP4
- Drop your MKV file onto the box above, or click to choose it. Your file stays on your device.
- MP4 is already selected. Optionally pick a quality preset or a smaller resolution to shrink the file.
- Click Convert, then download your MP4. Large MKV files take longer, because the work happens on your own hardware.
Why convert MKV to MP4 here
- Your file is never uploaded. There is no server to upload it to.
- Handles the many codecs an MKV can contain and writes a widely compatible H.264 MP4.
- No account, no email, no watermark and no daily limit.
- Resolution and quality options for when a large MKV needs to become a smaller MP4.
Frequently asked questions
- What happens to subtitles and extra audio tracks?
- The conversion keeps the main video and audio and produces a standard MP4. Embedded subtitle tracks and additional audio tracks are not carried across, because MP4 handles them differently from MKV. If you need a specific audio track or burned-in subtitles, a desktop tool is a better fit for now.
- Why will my MKV not play on my phone or Apple TV?
- MKV is a container many Apple and TV devices simply do not support, regardless of what is inside it. MP4 is the container they all understand, so converting fixes playback even when the underlying video is the same.
- Is the video re-encoded?
- Yes, this re-encodes to H.264 for the widest compatibility, so there is some quality change, though it is hard to see at the Balanced or Best preset. A pure remux with no re-encode is faster but only works when the MKV's codecs are already MP4-compatible; re-encoding always produces a file that plays.
- Is my file really not uploaded?
- No. Your file is read and converted on your own device and never sent anywhere. You can prove it: convert one MKV while online (depending on the codecs inside, this may download a compatibility engine once, about 32 MB), then switch to airplane mode and convert another. It still works, because everything needed is now on your machine.