MKV to MP4 Converter
Convert MKV to MP4 in seconds, right in your browser. Most MKV files already hold H.264, HEVC or AV1 video that an MP4 can carry as-is, so ProMedia re-wraps the streams instead of re-encoding them: the picture stays bit-for-bit identical, nothing is uploaded and there is no file-size limit. Only tracks MP4 cannot carry, such as DTS audio, are converted.
- Runs on your device
- WebCodecs · GPU
- FFmpeg
- Works offline
Updated
Drop your videos here
How to convert MKV to MP4
Step 1: Drop one or more MKV files on the box above, or tap it to pick them. OBS recordings and downloads work the same way.
Step 2: Leave Quality on Balanced. It is only used if a track has to be re-encoded.
Step 3: Press Convert. Compatible video and audio are copied; anything MP4 cannot hold is converted automatically.
Step 4: Download each MP4, or all of them as one ZIP.
Good to know
Settings explained
- Quality
- Only used when a stream has to be re-encoded. Compatible streams are copied with no quality loss.
- Faster: Smaller file, quickest export
- Balanced: Good quality at a sensible size
- Best quality: Largest file, slowest export
- Video codec
- Automatic copies the original video stream when the new format can hold it, so there is no quality loss.
- Automatic: Best codec the format and your device support
- H.264 (AVC): Plays everywhere
- H.265 (HEVC): About 35% smaller, newer devices
- VP9: Web / WebM
- AV1: Smallest files, slowest to encode
- Always re-encode
- Off: compatible streams are copied instantly and losslessly. On: every stream is re-encoded, which can fix playback glitches.
Formats
Batch-friendly: add many files and they are processed one after another — if one fails, the rest still finish.
How it runs
- Hardware video engine
- Video is decoded and encoded by your device’s media hardware through WebCodecs — usually several times faster than real time.
- FFmpeg (when needed)
- Older formats and a few filters use FFmpeg compiled to WebAssembly. It downloads once (about 31 MB) the first time it is needed and is cached for offline use.
MKV vs MP4: what actually changes
MKV and MP4 are containers: boxes that hold video, audio and subtitle tracks. Converting between them does not have to touch the video itself. What changes is which players, phones and editors will open the file.
| Feature | MKV (Matroska) | MP4 (MPEG-4 Part 14) |
|---|---|---|
| Typical video codecs | H.264, HEVC, AV1, VP9 and older ones such as MPEG-2 | H.264, HEVC, AV1 |
| Typical audio codecs | Almost anything: AAC, Opus, MP3, AC-3, DTS, FLAC | AAC (plays everywhere), Opus on newer players |
| Subtitles | Many tracks: SRT, ASS/SSA, image-based PGS | Limited; most players ignore them |
| Plays on iPhone, QuickTime, smart TVs | Rarely without an extra app | Yes |
| Opens in iMovie and most editors | Often not | Yes |
| Best for | Archiving, multi-language films, crash-safe OBS recordings | Sharing, uploading, editing and phones |
What is an MKV file?
An MKV file is a Matroska video: an open, royalty-free container that can hold any number of video, audio and subtitle tracks plus chapters and attached fonts in one file. That flexibility is why film rips, multi-language downloads and OBS Studio recordings use it. OBS users often record to MKV because a crash or power cut does not corrupt the whole file.
The catch is compatibility. iPhones, QuickTime, iMovie, many smart TVs and most upload forms expect MP4, so an MKV that plays fine in VLC can be refused everywhere else.
Remux or re-encode: what happens to each track
Remuxing copies the compressed video and audio into a new container without decoding them, so it is as fast as reading the file and loses nothing. Re-encoding decodes and compresses the picture again, which takes longer and always costs some quality. ProMedia remuxes every track it can and re-encodes only what MP4 cannot hold.
| Track in your MKV | What happens | Quality |
|---|---|---|
| H.264, HEVC or AV1 video | Copied into the MP4 (remux) | Identical to the original |
| AAC or Opus audio | Copied | Identical |
| MP3, AC-3 or DTS audio | Converted to AAC; the video is still copied | Video identical, audio transparent at normal bitrates |
| Older video such as MPEG-2 or Xvid | Re-encoded to H.264 (FFmpeg loads once if the browser cannot decode it) | Close to the original at Balanced or Best |
| Subtitle tracks and attached fonts | Not carried over to the MP4 | Save them first with Extract Subtitles |
Why convert MKV to MP4 with ProMedia
- No upload, no size cap. The file is read from your disk in chunks, so a multi-gigabyte film works on a desktop computer. Upload sites often stop at 1 GB or ask you to pay.
- Lossless by default. Compatible streams are copied, not re-encoded, so you keep the original picture and the conversion usually takes seconds rather than minutes.
- Batch-friendly. Drop a whole season or a folder of OBS recordings; each file is converted in turn and you can download them as one ZIP.
- Private and offline. Recordings of your screen or family never leave your device, and the converter keeps working in airplane mode after your first visit.
Convert MKV to MP4 on Windows, Mac, iPhone or Android
The converter runs in any modern browser, so the steps are the same everywhere. Only the way you pick and save files differs.
Windows 10 and 11
Open this page in Chrome, Edge or Firefox and drag the MKV files from File Explorer onto the drop zone. The MP4 files land in your Downloads folder.
Mac
QuickTime cannot open most MKV files. Drag them from Finder into Safari or Chrome here, convert, and the MP4 opens in QuickTime, Photos and iMovie.
iPhone and iPad
In Safari, tap the drop zone and choose Choose Files to pick the MKV from the Files app. Save the MP4 to Files, then share it to Photos. Very large files are limited by the phone’s memory.
Android
In Chrome, tap the drop zone and pick the MKV from your downloads or file manager. The MP4 is saved to Downloads and shows up in your gallery app.
Tips & troubleshooting
Need the subtitles? Save them as SRT with Extract Subtitles first, then put them back into the MP4 with Add Subtitles to Video.
If the MP4 stutters or will not play on an old TV or phone, switch on Always re-encode under Advanced settings. Every stream is then re-encoded, normally to H.264, which fixes most playback problems at the cost of time.
Remuxing keeps the file size. To make the MP4 smaller for sharing, run it through the video compressor and type the size you need.
Renaming .mkv to .mp4 does not convert anything: the file is still Matroska inside, and most players will refuse it.
Converting OBS recordings? Keep recording to MKV for crash safety and convert afterwards, a whole folder at a time.
Only need the soundtrack of a film or recording? MKV to MP3 saves just the audio instead of converting the video.
MKV to MP4 Converter FAQ
Does converting MKV to MP4 lose quality?
Not when the codecs fit, which covers most MKV files. H.264, HEVC and AV1 video is copied into the MP4 unchanged, so the picture is bit-for-bit identical. Only tracks MP4 cannot hold, such as DTS audio or MPEG-2 video, are re-encoded, and ProMedia tells you which ones on the result card.
Can I just rename .mkv to .mp4?
No. The extension is only a label; the data inside is still a Matroska container, so most phones, TVs and editors will refuse to open it. Converting here takes about as long as copying the file because the streams are re-wrapped, not re-encoded.
Why is MKV to MP4 so fast here?
Because nothing is re-encoded when it does not need to be. If the video is H.264, HEVC or AV1 and the audio is AAC or Opus, the streams are copied into an MP4 box as-is. Other audio (MP3, AC-3, DTS…) is converted to AAC while the video is still copied.
What happens to subtitles and extra audio tracks?
Extra audio tracks are kept when the browser can decode them: AAC and Opus are copied, others become AAC. If the main audio is DTS, the FFmpeg engine keeps only the first track. Subtitle tracks are not carried over, so save them as SRT with Extract Subtitles before converting.
My MKV has DTS or AC-3 audio. Will it work?
Yes. Those audio codecs are converted to AAC so the MP4 plays on phones and browsers, while the video stream is still copied without loss.
How do I convert MKV to MP4 on my phone?
Open this page in Safari on iPhone or Chrome on Android, tap the drop zone and pick the MKV from Files or your downloads. Conversion happens on the phone itself. Files of several gigabytes are best done on a computer because phones have less memory.
Is there a file size limit?
There is no upload limit because there is no upload. Videos are read in chunks straight from disk, so multi-gigabyte files work on desktop computers; phones are limited by their memory. There are no daily caps and no watermark.