Video / Convert
MKV to MP4 — Local Browser Tool
Convert a playable MKV to MP4 on your device, with recording support checks, progress, cancellation and an output preview.
MKV to MP4 — Local Browser Tool: Matroska files can contain several video, audio and subtitle tracks. Browsers do not support every combination, and some cannot open MKV at all. The actual source is tested when you start conversion. If decoding fails, use a desktop application with Matroska support. Renaming MKV to MP4 does not change its contents. Conversion plays the source into a new recording at playback speed. It keeps the original dimensions by default, or you can choose an output height of 1080, 720 or 480 pixels. A smaller source is not enlarged. The normal soundtrack is routed into the recording; additional audio tracks, chapters, subtitles and container metadata are not copied. Keep this tab visible until conversion finishes. A progress indicator shows the recording advancing, and Cancel discards the current job. The output size appears beside the download after conversion. A different container does not guarantee a smaller file: the result is re-encoded and may be larger or lower in quality. Files must be smaller than 250 MB and have a readable duration of no more than ten minutes. The source image area must be no larger than 3840 × 2160. Protected media cannot be converted. Keep your original file until you have checked the downloaded video and its sound in the application that needs it. Runs 100% locally in your browser with zero server file uploads.
- Category
- Video tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
Click, drag and drop, or paste · stays on this device
Files stay on this device. Up to 250 MB, ten minutes and 3840 × 2160 pixels in area. Video is re-recorded at playback speed. Keep this tab in the foreground; the result may be larger or lose quality.
The actual file is tested for decoding when conversion starts. MKV and AVI may not play in this browser. Protected video and unsupported codecs cannot be converted.
Checking recording support…
Browser codecs and recording
A filename identifies a container, not the codec inside it. The browser must decode the source and support the requested recording format. The HTML media specification (https://html.spec.whatwg.org/multipage/media.html) describes local playback, and the recording specification (https://www.w3.org/TR/mediastream-recording/) describes supported output types.
Local conversion limits
Conversion accepts files smaller than 250 MB and readable videos up to ten minutes, with an image area no larger than 3840 × 2160. Recording takes about the clip duration and needs the tab kept in front. Size and quality can change; subtitles, extra tracks and metadata are not retained.
How to use it
- Choose a file in the input format shown.
- Adjust the available output controls.
- Create the result, check its preview and download it.
Privacy & limitations
Your file is processed on this device. No image, video or audio is uploaded.
Related tools
Frequently asked questions
Will every MKV file work?
Matroska files can contain several video, audio and subtitle tracks. Browsers do not support every combination, and some cannot open MKV at all. The actual source is tested when you start conversion. If decoding fails, use a desktop application with Matroska support. Renaming MKV to MP4 does not change its contents.
Is conversion instant or lossless?
No. It creates a fresh recording at playback speed, so a one-minute clip takes about a minute to encode. It can lose detail and does not preserve extra tracks, subtitles or metadata.
What if MP4 recording is unavailable?
The page shows a clear support message and disables conversion. Use a browser that can record the requested format or a desktop converter. It never substitutes a file with the wrong container.
Free tool · runs in your browser · no account required