MP4 to MKV Converter
MKV (Matroska) is the container media-server fans and archivists prefer, because it can carry any codec, many audio and subtitle tracks and chapters. This page writes your MP4 into an MKV at near-original quality with the sound left untouched.
Video Converter
or drop MP4, MOV, MKV … files here ·
Max 95 MB per file· Up to 20 files· Deleted after 30 minutes
Files are processed on our servers and deleted after 30 minutes.
Lower is better quality and a bigger file. 18 looks identical to the source, 23 is the default, 28 and above shows visible softening.
Frames per second. Keep the source rate unless a platform asks for a specific one; 15–20 fps is plenty for GIFs.
Only used for PowerPoint files and single still images: how long each slide or picture stays on screen.
Auto uses AAC for MP4/MOV and Opus for WebM. Copy keeps the original sound untouched when the new format supports it.
192 kbps is transparent for music; 128 kbps is enough for speech.
Width of the animation in pixels; height follows the aspect ratio. 480 px suits chats, 720 px or more gives a high-quality GIF but a much larger file.
GIF holds at most 256 colors. Fewer colors make a smaller file but cause banding on gradients and skin tones.
Mixes palette colors in a fine pattern to hide banding. Sierra gives the smoothest result; none gives the smallest file.
Whether the animation repeats endlessly or plays one time and stops.
Optional. Seconds (e.g. 75) or minutes:seconds (1:15). Leave empty to start at the beginning.
Optional. Same format as the start time. Leave empty to keep everything up to the end.
The converted file will be at or just under this size.
How to use this tool
- 1
Add your MP4 files
Drop up to 20 videos on the upload area, each up to 95 MB.
- 2
Keep the archive settings
The page starts on Video codec H.264 at Quality (CRF) 18 and Audio codec Copy original. Pick H.265 if you want a smaller library file.
- 3
Convert and download
Press Convert to MKV and move the files into your media folder.
Should I convert MP4 to MKV?
Convert when the file is headed for VLC, Plex, Kodi or an archive drive where you will add subtitles or extra audio later. Keep the MP4 for iPhones, social apps and video editors.
MKV vs MP4: what the Matroska container adds
Matroska started in 2002 as an open project and uses EBML, a binary relative of XML, to describe what each file contains. That design lets an MKV carry almost any video and audio codec, any number of tracks, text and bitmap subtitles, chapter markers and even attached fonts. Google built WebM on a subset of Matroska in 2010.
MP4 is stricter. It was standardized for interoperability, so phones, browsers and editors play it with no surprises, but it holds subtitles only as simple timed text and rarely more than a couple of audio tracks in practice. For a movie folder with three languages and styled anime subtitles, that is a limit; for a clip sent to a friend, it is irrelevant.
MP4
MPEG-4 video
MP4 (MPEG-4 Part 14) is a multimedia container standardised by ISO/MPEG and based on Apple's QuickTime format. It usually holds H.264 or HEVC video with AAC audio, and can also carry subtitles, chapters and metadata. It is the most compatible video format in the world, playing on phones, browsers, TVs, game consoles and social platforms. The video inside is almost always lossy, so repeated re-encoding gradually reduces quality.
- Compression
- Lossy
- Transparency
- –
- Animation
- –
- Introduced
- 2001 · Moving Picture Experts Group (MPEG)
MKV
Matroska video
MKV is the Matroska multimedia container, an open-source format first released in 2002. It can hold nearly any video and audio codec plus unlimited audio tracks, subtitle tracks, chapters and attachments in one file. That flexibility makes it popular for films with several languages, screen recordings from OBS and long-term archiving. Phones, browsers, editors and some TVs do not support MKV, even when they support the codec inside.
- Compression
- Lossy or lossless
- Transparency
- –
- Animation
- –
- Introduced
- 2002 · Matroska project
MP4 goes to MKV when the file is joining a media library or an archive, where room for extra subtitle and audio tracks and chapters matters more than playing on every phone.
Convert MP4 to MKV for VLC, Plex and Kodi
MKV is a good fit for
- VLC, mpv and Kodi on any computer
- Plex and Jellyfin libraries
- Windows 10 and 11 Films & TV and Media Player
- Archives that will gain subtitle tracks later
MKV is a poor fit for
- iPhone and iPad built-in apps
- QuickTime Player on a Mac
- iMovie, Final Cut Pro and most phone editors
- Instagram, TikTok and other upload forms
| from ↓ · to → | MKV | MP4 |
|---|---|---|
| Several audio languages | Several audio languages to MKV: yes | Several audio languages to MP4: yes |
| SRT or ASS subtitles | SRT or ASS subtitles to MKV: yes | – SRT or ASS subtitles to MP4: no |
| Chapters | Chapters to MKV: yes | Chapters to MP4: yes |
| Attached fonts | Attached fonts to MKV: yes | – Attached fonts to MP4: no |
| iPhone Photos playback | – iPhone Photos playback to MKV: no | iPhone Photos playback to MP4: yes |
Remux or re-encode: getting the MKV you expect
Remuxing copies the video and audio bit for bit into the new container; re-encoding decodes and compresses them again. This page re-encodes the picture, so you can change codec or resolution on the way, and copies the sound so nothing changes there. At CRF 18 the difference from the source is not visible; the file may come out a little larger or smaller than the MP4.
To shrink a library, switch Video codec to H.265 and leave CRF at 18 to 22. To cut a long recording first, fill Start at and End at. For the reverse trip, or for any other source format, open the video converter or AVI to MKV for old camera files.
MP4 to MKV questions
Is MKV better quality than MP4?
Neither container has a quality of its own; the codec and its settings decide that. An H.264 stream looks identical in either box. MKV wins on flexibility, MP4 on how many devices play it.
Does converting MP4 to MKV re-encode the video?
Here, yes: the video is encoded again with the codec and Quality (CRF) you choose, which is why the page starts at CRF 18, visually the same as the source. The audio is copied untouched. A pure remux, which only moves the streams into a new box, needs a desktop tool such as MKVToolNix.
Will an MKV play on my iPhone?
Not in the Photos app, the Files preview or the Apple TV app; iOS has no MKV support built in. Players such as VLC for iOS and Infuse open it. If the video is meant for an iPhone, keep the MP4.
How do I add subtitles to the MKV?
This converter writes the video and the audio track. Open the resulting MKV in MKVToolNix, add your .srt or .ass file as a new track, give it a language and save; VLC and Plex then offer it in their subtitle menu.
Should I use H.265 for an MKV library?
If every player in the house is recent, yes: H.265 typically needs about half the space of H.264 for the same picture. Older streaming sticks and laptops may stutter, and Plex will transcode for them, which costs server power.
Can I go back from MKV to MP4 later?
Yes, with MKV to MP4. Any extra tracks you added after conversion are dropped on the way back, because MP4 cannot hold most subtitle formats.
- MKV to MP4 ConverterConvert MKV to MP4 free online. Turns OBS recordings and Matroska files into H.264/AAC MP4 that iMovie, iPhones and smart TVs open. Up to 20 files.
- AVI to MKV ConverterRewrap old AVI files from DivX, Xvid and DV captures into MKV for Plex, Kodi and VLC, with H.264 video and the original soundtrack kept. No account.
- MP4 to WebM ConverterConvert MP4 to WebM for HTML5 video, background loops, Wikimedia Commons and Telegram stickers. Opus audio, adjustable CRF, trim and size limit built in.
- MP4 to MOV ConverterConvert MP4 to MOV online for QuickTime, Final Cut and agency deliverables that ask for .mov. Quality set to CRF 18 so the copy is ready to edit.
- MP4 to HEVC ConverterShrink H.264 MP4 videos by re-encoding them to HEVC (H.265) at CRF 28, the x265 default. Saves storage on phones, NAS drives and backups. No account.
- MP4 to WMV ConverterConvert MP4 to WMV for PowerPoint 2010, Windows Movie Maker and Windows Media Player on XP or Vista. Up to 20 files of 95 MB, deleted after 30 minutes.