Spoolfield for Windows
Convert MKV to MP4 on Windows
MKV files often won’t open on phones, TVs or in some editors, while MP4 plays almost everywhere. Spoolfield turns MKV into MP4 on your PC. When the video and audio inside already suit MP4, it just moves them into the new file, which takes seconds and loses nothing.
Free for a day, up to 3 files, no card. Your MKV file is never changed.
MKV to MP4 in 3 steps
- Open Spoolfield and switch to Convert files. Drop in one MKV or a whole folder’s worth, or click Choose files.
- Choose MP4. Leave File size on Original to keep the full quality.
- Click Convert. The MP4 copies are saved to your Spoolfield folder, and your MKV files stay where they were.
Fast when it can be, careful when it can’t
Repackaged, not re-encoded
Many MKV files already hold H.264 video and AAC audio. Spoolfield moves those streams into an MP4 file as they are, with no quality loss.
Converted when needed
When something inside doesn’t suit MP4, Spoolfield converts just that part, so the file plays in phones, TVs and editors.
Many files in one go
Add as many files as you like. They line up in the queue and convert one after another.
Other formats too
The same tab turns videos into MOV, MKV or WebM, keeps the sound as MP3, M4A or WAV, and converts images to JPG, PNG or WebP.
Questions
Will converting MKV to MP4 lose quality?
Not when the streams can be repackaged, which is the case for most MKV files with H.264 video and AAC audio. If a stream has to be converted, Spoolfield re-encodes it at high quality, and you can keep your MKV as a backup because it’s never changed.
Why is my MKV converting slowly?
Its video or audio doesn’t fit MP4 as it is, so Spoolfield has to re-encode it. Long or high-resolution videos take longer. Repackaging, when it’s possible, takes seconds.
Can I make the MP4 smaller at the same time?
Yes. Under File size, choose 25 MB, 16 MB or 10 MB, or Custom with your own size in MB. Spoolfield fits the video to that size, so expect lower quality for long videos.
Does it work offline?
The conversion runs on your PC and doesn’t send your file anywhere. Spoolfield does need the internet about once a day to check your trial or subscription.
Turn your MKV files into MP4
Free for a day, up to 3 files. No card, no account.
Converting is included in both plans, even Lite, the plan for converting only. Saving clips from nine sites comes with Pro. Only download content you own or have permission to use.