How to Convert MKV to MP4 (Play on Phones and TVs)
MKV files won't play on many phones and TVs. Convert to MP4, often without re-encoding. Note: subtitle tracks aren't kept. Try it with a free account.
Published ยท 5 min read
To convert MKV to MP4, move the video and sound into an MP4 container, and re-encode them only if the phone or TV can't play the formats inside. Our MOV to MP4 converter handles MKV too and makes that choice for you: if the MKV already holds H.264 video, it's repackaged without any quality change. One thing to know first: the MP4 keeps one video and one audio track, so separate subtitle tracks are not carried over. It's a pro tool you can try with a free account on videos up to 30 seconds.
Why MKV files won't play
MKV (Matroska) is a flexible "container": a box that can hold almost any video format, several audio tracks (say, English and Hindi), subtitle tracks and chapter markers. Screen recorders such as OBS can save in it, and it's popular for videos with multiple languages.
That flexibility is also the problem. iPhones, iPads, many smart TVs, some Android phones and plenty of editing apps don't support MKV at all, or play the video but not the sound. MP4 with H.264 video and AAC sound is the format almost everything supports. For the full comparison, see MKV vs MP4.
Step by step
- Open the MOV to MP4 converter and sign in.
- Under Choose a file, pick your MKV, up to 1 GB and 30 minutes.
- Press Start and wait while it converts.
- Press Download result to save the MP4. It's kept for 1 hour.
There are no settings. Before uploading, the page reads the video's length in your browser. Chrome and Edge can usually read MKV files; if your browser can't, you'll see "We couldn't read that file." Try again in Chrome or Edge.
Repackaged or re-encoded?
The converter looks inside the MKV and picks the route:
| What's inside the MKV | What happens | Quality |
|---|---|---|
| H.264 video, at a typical size for its length | Moved into MP4 as it is | Unchanged; fast |
| HEVC (H.265), VP9, AV1 or another format | Re-encoded as H.264 at high quality | Very close to the original; above 1080p is scaled to 1080p |
| H.264 at an unusually high bitrate | Re-encoded as H.264 at high quality | Very close to the original, and smaller |
Sound in AAC or MP3 is copied as it is. Other sound formats common in MKV files, such as AC3, DTS, Opus or Vorbis, are converted to AAC, the standard MP4 sound format, so it plays everywhere.
If you want to know why HEVC or VP9 needs re-encoding while H.264 doesn't, our explainer on what a video codec is covers it.
What about subtitles and extra audio tracks?
This is the main thing to check before converting:
- Subtitle tracks are not kept. If the MKV has subtitles you switch on and off in the player, the MP4 won't have them. Subtitles that are part of the picture itself ("burned in") stay, because they're just part of the video.
- Only the first audio track is kept. If the MKV has several languages, the MP4 gets the first one, which is usually the default. If you need a different language, set it as the first track in an MKV tool before converting.
If subtitles matter, keep a separate copy of the subtitle file (an SRT, which many MKV tools can extract). Most players on computers and TVs can load an SRT alongside an MP4 with the same name. For your own recordings with no subtitles at all, our subtitle generator can make an SRT from the speech (a pro tool, free to try on videos up to 30 seconds); see how to add subtitles to a video.
OBS recordings: a tip
If you record your screen or games in OBS, MKV is a sensible recording format because the file survives a crash. OBS can also remux MKV to MP4 itself (File > Remux Recordings), which is instant and keeps everything. Use our converter when you're on another computer, or when the MKV needs re-encoding to play somewhere.
Need it smaller?
Repackaging keeps the file about the same size. If you're sending the video on WhatsApp, email or Discord, use the video compressor instead: it also takes MKV and gives you a smaller MP4 in one step. See how to compress a video without losing quality.
Trying it free
MOV to MP4 is a pro tool. A free account can try it on videos up to 30 seconds, and you get 5 free tries a day across all our pro tools. Longer videos, up to 30 minutes and 1 GB, need a paid plan.
Your files and privacy
Conversion runs on our servers, so your video is uploaded. It's deleted as soon as it's converted, and your MP4 is available to download for 1 hour, then deleted too.
Convert your MKV
Choose your MKV in the MOV to MP4 converter, press Start and download an MP4 that plays on phones and TVs. Clips up to 30 seconds can be tried with a free account.
Frequently asked questions
- Does converting MKV to MP4 lose quality?
- Not when the MKV holds H.264 video at a normal size: it's repackaged without changes. Other formats are re-encoded at high quality, which is very hard to tell apart from the original.
- Will my subtitles carry over to the MP4?
- No. Subtitle tracks and extra audio tracks are left out; the MP4 has one video and one audio track. Burned-in subtitles stay because they're part of the picture.
- Which audio language will the MP4 have?
- The first audio track in the MKV, which is usually the default one.
- Why won't my MKV play on my iPhone or TV?
- Many devices don't support the MKV container or the formats inside it. MP4 with H.264 and AAC plays on almost all of them.
- Is MKV better than MP4?
- MKV is more flexible (many tracks, subtitles, chapters); MP4 is more compatible. Keep the MKV as your archive copy and share the MP4.
Video tools
Try MOV to MP4
Free to try with a free account. Convert MOV, MKV, WEBM and other videos to MP4, the format that plays on almost every phone, computer and website.