# MKV to MP4 Converter > Browser-only file conversion. Selected files are processed on this device and are not uploaded to a conversion server. Source: https://localconverter.tech/mkv-to-mp4 Re-encode MKV media as MP4 using the browser conversion engines. Choose a compatible container for your player or editor, and trim the source when you only need a specific passage. Re-encoding can change quality and size; switching extensions cannot recover detail already missing from the recording. ## Useful tasks - Make a MP4 copy for a player or editor that needs this format. - Export a selected passage rather than the entire recording. - Keep the source while preparing a separate delivery copy. ## Steps 1. **Select your MKV files**: Use Select File or drop supported MKV files into the upload area. Each file creates a separate MP4 result. Check that the filename extension matches the contents and that the original opens correctly before adding a larger batch. 2. **Choose the output settings**: Open Options beside a selected file. Start time, Duration, Width, Video quality are available for this MKV to MP4 operation. Save options to apply them to that file; other files in a batch can use different settings. 3. **Convert to MP4**: Select Convert to add the files to the local queue. Files run one at a time, with real progress where the engine provides it. You can cancel a queued or running job and retry a failed result after correcting its input or settings. 4. **Download and check the result**: Selections and completed jobs stay available while you navigate inside this tab. Use My files to revisit results. Reloading or closing the tab clears the workspace; download results you want to keep first. ## Settings - **Start time (seconds)**: Set where the conversion begins, measured in seconds from the start of the file. Default: 0. - **Duration (seconds; 0 keeps remaining)**: Set how many seconds to convert. Use 0 to include the rest of the file. Default: 0. - **Width (pixels; 0 keeps original)**: Set the output width in pixels. Use 0 to keep the original width; proportions are retained. Default: 0. - **Video quality (lower is better)**: Set video compression quality. Lower values keep more detail and usually produce larger files. Default: 23. ## Start with one representative passage For a recording longer than 20 seconds, set Start to 5 and Duration to 10 to export the passage from second 5 to second 15. Review the default output before changing quality or dimensions. Use Duration 0 when you want the remaining recording. ## Check the result Play the saved file in the app you intend to use. Check the beginning and end, orientation, audio/video synchronisation and whether the required track is present. Only the first supported streams are used and metadata is removed. Inputs can be up to two hours; processing still has a job deadline. ## About MKV Stores video and audio in a Matroska container. Local output uses H.264 video and AAC audio. ## About MP4 Stores video and audio in a widely supported container. Local output uses H.264 video and AAC audio. ## Limits - Files are processed on this device. Browser memory and engine-specific limits apply. Save results before reloading. - Only first video/audio streams; media is re-encoded, metadata removed. - Audio extraction requires an audio track. GIF has no audio. - Input duration limited to two hours; MP4/MOV/MKV use H.264/AAC, WebM uses VP9/Opus. - Processing runs in this browser. Large files may exceed your device memory; save results before reloading. - Up to 20 files per session, 100 MB per file and 200 MB per output. Processing has a 180-second job deadline. ## Questions ### How do I convert MKV to MP4? Choose your MKV files, review Options and the format notes, then select Convert. Download the finished MP4 copy and check it in your destination application. Each input is processed independently; the original file remains unchanged. ### Will the output look exactly like the original? That depends on the source and output formats. Review the format limits above for details about layout, styling and content that may change. ### Which settings can I change for MKV to MP4? Start time (seconds): Set where the conversion begins, measured in seconds from the start of the file. Default: 0. Duration (seconds; 0 keeps remaining): Set how many seconds to convert. Use 0 to include the rest of the file. Default: 0. Width (pixels; 0 keeps original): Set the output width in pixels. Use 0 to keep the original width; proportions are retained. Default: 0. Video quality (lower is better): Set video compression quality. Lower values keep more detail and usually produce larger files. Default: 23. ### Will the result be smaller or better quality? A successful MP4 conversion does not guarantee a smaller file or recovered detail. Container overhead, compression and the selected settings all affect output size. Check the saved result and keep the source if you might need a different export. ### Why did my MKV file fail? Read the message beside the file. A mismatched extension, corrupt data, unsupported feature or resource limit can prevent conversion. Check that the source opens normally, try the default settings and retry. The app will not offer a successful download for a failed job. ### Where are files processed and how long are they kept? Processing runs in this browser, on your device. Files and pasted input are not uploaded to a conversion server. The website and required engine assets must load first; large operations depend on available device memory. ## Related guides - [MKV to WEBM](https://localconverter.tech/mkv-to-webm.md) - [MKV to MOV](https://localconverter.tech/mkv-to-mov.md) - [MKV to GIF](https://localconverter.tech/mkv-to-gif.md) - [MKV to MP3](https://localconverter.tech/mkv-to-mp3.md)