MKV to MP4 Converter
To convert MKV to MP4 here, drop the file on the page: H.264 video and AAC audio are copied into the MP4 without re-encoding, other codecs are converted, and nothing is uploaded. The MP4 keeps the main video track and the main audio track, so subtitles and extra languages stay behind.
- Free
- No sign-up
- No watermark
- Runs in your browser
Loading the tool.
What an MKV holds and what the MP4 gets
MKV is a container that takes almost any codec, so what this page does depends on what is inside your file. A screen recorder such as OBS Studio, a downloaded video or a movie file can each produce an MKV with different codecs. When you drop the file, the page reads it and prints the container as MKV (Matroska) together with the codecs it found. The table follows each part of an MKV through the converter.
| Inside the MKV | What the page does | What you get in the MP4 |
|---|---|---|
| H.264 video | Copies it into the MP4 as it is | The same picture, finished as fast as the file can be read |
| AAC audio | Copies it as it is | The same sound |
| HEVC, VP9 or AV1 video | Decodes it and encodes H.264, if your browser can decode that codec | A picture that plays on more devices, after a longer wait |
| Opus or Vorbis audio | Decodes it and encodes AAC | AAC sound, the audio codec MP4 players expect |
| Dolby Digital (AC-3, E-AC-3) or DTS audio | Stops with a message that names the audio codec | No file, because most browsers cannot decode these |
| A second language, subtitle tracks, chapters | Leaves them out | One video track and one audio track |
The page works from the main video track and the main audio track of the file and offers no menu for picking another one. After the run, a line under the result says whether the video and the audio were copied or re-encoded, and frame size and frame rate stay as they were.
Where MKV files come from
Screen and game recorders such as OBS Studio can save to MKV. Downloaded videos and movie files are often MKV as well, because the container takes any codec and any number of audio and subtitle tracks. That freedom is also why one MKV converts in seconds and another needs a long re-encode: the container says nothing about the codecs inside, and the page has to look at them one by one.
One audio track and no subtitles
The MP4 made here has one video track and one audio track. A movie MKV with two languages therefore gives you its main audio track, and the page has no menu for picking the other. Subtitle tracks and chapters are not written to the MP4 at all. Everything the MKV stores beside its main picture and sound stays in the original file, which the page never changes.
Movie soundtracks that browsers cannot play
Movie MKV files often carry Dolby Digital or DTS sound. Browsers generally cannot decode those codecs, and this page does not drop the sound without telling you. It stops, names the audio codec and explains why. A file like that needs its sound changed to AAC in a desktop program before this converter can take it, while an MKV with AAC or Opus sound converts here.
How big an MKV the page can take
Game and screen recordings in MKV are often large, and the tool puts no cap on the size. It reads the MKV from your disk in small slices, so a multi-gigabyte file does not have to be loaded first. The MP4 is built in memory until you download it, and after a copy it is about as big as the MKV. If the tab runs out of memory the page says so and suggests closing other tabs.
Questions people ask
How do I convert MKV to MP4 without re-encoding?
Open the MKV, leave MP4 selected and read the sentence under the format choice. If it says the streams will be copied, the video is H.264 and the audio is AAC, and the new MP4 holds the original data unchanged. If it says re-encoded, a codec did not fit MP4, and the sentence says which one.
Why does my MKV to MP4 conversion stop with an audio error?
The soundtrack is probably Dolby Digital or DTS, which browsers generally cannot decode. The page stops and names the codec instead of making an MP4 without sound. To convert that file, change its audio to AAC in a desktop program first, or start from a version with AAC or Opus sound.
Can I keep the subtitles when I convert MKV to MP4?
No. Only the main video track and the main audio track are written to the MP4, so subtitle tracks, extra audio languages and chapters are left behind. The converter does not offer a choice of tracks, and your original MKV is not changed.
Is there a file size limit for MKV to MP4?
The tool sets none. The MKV is read from your disk in slices, but the finished MP4 is built in memory, so the limit is the free memory of your device. A copy comes out about as large as the MKV. If memory runs out, the page says so and you can close other tabs and try again.
What to do with a long recording
An MKV from a screen or game recorder is often an hour long or more. GPT-Video takes a long recording like that and cuts it into short vertical clips, reframes them around the speaker's face and adds captions. That job runs on our servers and uses credits.
Related
Your file is processed on your device and never uploaded.