FileDial › Guides › Video and subtitles
How to convert MKV to MP4 on a Mac
By Himanshu Ranjan · Updated 8 November 2026
QuickTime Player does not open MKV files. To convert MKV to MP4 on a Mac, select the file in Finder, hold the right Option key and run FileDial's Convert › Convert to MP4. It makes a new MP4 beside the original, offline, with nothing uploaded. Keep the MKV if you need its extra tracks.
Why MKV causes trouble on a Mac
Matroska, the format behind .mkv files, is an open container that can hold many video, audio and subtitle tracks plus chapters in one file. That flexibility is why it is popular for downloads and rips. It is also why Apple's apps do not open it: QuickTime Player and Photos expect MP4 or MOV.
A container is the wrapper, not the picture itself. The video inside an MKV might be H.264 or HEVC, which Apple software handles well, but the wrapper stops it from opening. Converting to MP4 changes the wrapper and may also re-encode the video, depending on the tool.
Convert with FileDial
One tool does the conversion. It creates a new MP4 copy and leaves your MKV where it is.
- In Finder, select one or more MKV files. Batches work, so you can select a whole folder's worth.
- Hold the right Option key to open the dial, or right-click and choose Open in FileDial.
- Choose Convert › Convert to MP4.
- Open the new MP4 from the same folder in QuickTime Player, iMovie or Photos.
What you might lose
An MP4 can hold several audio tracks and subtitle tracks, but not every kind of subtitle or chapter layout survives a conversion. If your MKV has multiple language tracks or soft subtitles you want to keep, check the result before deleting the original. FileDial's Convert › Extract subtitle tracks saves each text track from a video as an SRT, so you can keep the subtitles separately.
If you want the subtitles visible in the picture, Combine › Burn in subtitles takes a video and an SRT or VTT file and makes a copy with the text baked in. The extract-subtitles guide covers that route.
Which MKV files need converting
Not every MKV needs conversion. If you only watch on your Mac, a player that supports Matroska is enough and leaves the file untouched. You need an MP4 when you want to open the video in QuickTime Player, edit in iMovie, add it to Photos, post it to a service that rejects MKV or send it to someone on an iPhone.
Large MKV files, such as recorded streams or long rips, may take a while to convert. Run the batch while you do something else, and check the first result before queuing a whole folder.
After converting
Once the MP4 plays well, you can shrink it further. Compress › Compress to 1080p or Convert › Convert to HEVC (smaller) cut the size, and the compress-video guide lists the options. If the MKV had chapters you care about, remember that Cut › Split by chapters makes one file per chapter without re-encoding, which is another way to use that structure.
If a particular file refuses to convert, it may be damaged or protected. Try playing it in another player first to confirm it opens at all.
Container, codec and trade-offs
It helps to keep three words straight. The container is MKV or MP4, the codec is what compresses the picture, such as H.264 or HEVC, and the tracks are the pictures, sounds and subtitles inside. Wikipedia describes Matroska as a container that can hold an unlimited number of video, audio, picture or subtitle tracks, which is why MKV files from disc rips or streams often carry several languages and chapters.
The trade-off is simple. MKV keeps all of that structure and is the better archive. MP4 gives you compatibility with Apple software, phones and most upload forms but may not keep every track. A good habit is to keep the MKV as the master and treat the MP4 as the copy you edit or share. Do not delete the MKV just because the MP4 plays.
FileDial is the right tool when you have one file or a folder to convert and want it done without an upload. It is not the right tool for picking apart individual tracks inside a file or editing chapters, where a dedicated Matroska tool does more.
Free alternatives
On a Mac the built-in apps will not help with MKV directly. Players such as VLC open it without conversion, which is the best choice if you only want to watch. Conversion matters when you need to edit in iMovie, upload somewhere that wants MP4, or share with someone on an iPhone.
Online converters are the other common route. They require uploading the whole video, which can be gigabytes, and the FBI has warned that free online converter sites are increasingly used to spread malware. Converting on your Mac avoids both the wait and the risk.
Questions
Can QuickTime Player open MKV files?
No. QuickTime Player and Photos do not play MKV files on a Mac. Convert the file to MP4 or open it in a player that supports Matroska. FileDial's Convert › Convert to MP4 makes the MP4 copy and keeps the MKV. Players such as VLC can play MKV directly, so conversion is only needed when you want Apple apps or an MP4-only service to open it.
Will converting MKV to MP4 lower quality?
It depends on how the conversion is done, since a container change alone need not touch the picture while a re-encode does. Keep the original MKV until you have checked the MP4 plays as you expect. It depends on how the conversion is done, since changing the wrapper alone leaves the picture alone while re-encoding does not.
What happens to subtitles in my MKV?
MP4 does not carry every subtitle type an MKV can. Use Convert › Extract subtitle tracks to save each text track as an SRT, or Combine › Burn in subtitles to bake them into the picture. Soft subtitles are the part most likely to change, so test the MP4 in the player you will actually use.
Can I convert many MKV files at once?
Yes. FileDial works in batches: select several files in Finder and run Convert › Convert to MP4 on all of them. Each gets its own new MP4 beside the original. Each file gets its own MP4, so one problem file does not spoil the rest, and the originals stay untouched.