MP4 to MKV converter
A free MP4 to MKV converter for MPEG-4 Part 14 files. Browser-based pairs here usually run in this tab, with no file upload.
Drop your MP4 files here
or browse your device · paste with Ctrl+V
Accepts .mp4 files. You can queue several files; each is processed one after another on your own device.
Your files never leave this device — there is no upload and no server to delete them from.
- 01
Add your MP4 files
Drop them onto the box above or click to browse. They are read straight from disk — nothing is sent anywhere.
- 02
Check the settings
MKV is already selected. Open the gear icon on any row if you want to change quality, dimensions or codec before converting.
- 03
Download your MKV
Press convert and wait for the row to finish. Convert several files and you can take them all as a single ZIP.
MP4
MPEG-4 Part 14The universal video container. H.264 video with AAC audio inside an MP4 plays on essentially every phone, browser, TV and editor made in the last fifteen years, which is why it is the safe default for sharing and uploading.
- Developed by
- ISO/IEC (MPEG)
- Released
- 2001
- Extension
- .mp4
- MIME type
- video/mp4
- Compression
- Lossy
- Specification
- Open
MKV
Matroska VideoAn open container with no practical limits: unlimited audio tracks, subtitle tracks, chapters and attachments in one file. Favoured for archived films because it preserves everything, though native browser support is thin.
- Developed by
- Matroska (CoreCodec)
- Released
- 2002
- Extension
- .mkv
- MIME type
- video/x-matroska
- Compression
- Lossy
- Specification
- Open
- Both MP4 and MKV are lossy formats, so repeated conversions can accumulate rounding artifacts. Keep this to only what you need and avoid repeated round-trips.
Questions about converting MP4 to MKV
Is this MP4 to MKV converter free?
Yes. Converting MP4 to MKV here is free, with no account, no watermark and no daily quota. The work runs on your own device, so there is no server cost to pass on to you.
Is my MP4 file uploaded anywhere?
For browser-based pairs, your file is read locally and converted by ffmpeg in this tab. No file payload is uploaded; you may still see analytics and engine downloads in network logs.
Is there a file-size limit for MP4 to MKV?
There is no imposed upload cap when it runs in-browser, but each conversion still depends on your device and browser memory. Large videos are the first practical limit, then memory-heavy documents or images.
Does converting MP4 to MKV lose quality?
MKV is a lossy format, so some detail is discarded when it is encoded. At the default quality setting the change is often not visually obvious; keep your original MP4 file if you might need it again.
Can I convert several MP4 files to MKV at once?
Yes. Drop in several files and each gets its own row; they are processed one after another on your device. You can download them one by one or as one ZIP.
Does MP4 to MKV work on a phone, Mac or Chromebook?
Most modern browsers on Windows, macOS, Linux, ChromeOS, Android and iOS work. Very large videos are often more reliable on desktop or a browser with more memory.
Why do some conversions take longer on first run?
The conversion engine has to download first. Small codec bundles are fast, while ffmpeg is commonly 12–30 MB; later conversions of similar type use the cached engine.
I converted a file and the output is blank or unusable. What should I check?
Start over with default settings, then change one option at a time (quality, bitrate, page size, or codec) to isolate what changed behavior. If it keeps failing, retry with a smaller file and confirm the source format matches the pair.
Convert other formats to MKV
21 formats can become MKV here.
Convert MP4 to other formats
A MP4 file can become any of these.
MKV to MP4
The reverse conversion
MP4 to MP3
MP4 to WAV
MP4 to MOV
Compress Video
Reduce a video's file size with a quality dial you c…
Discord Video Compressor
Free Discord compressor — shrink any clip under Disc…
Trim Video
Cut a clip out of a longer video.…
Video to GIF
Turn a clip into an animated GIF with a proper colou…