MP4 to MKV Converter - For Archiving in VLC and Plex

MP4 is built for sharing, while MKV is built for keeping. This free mp4 to mkv converter re-encodes your video into the open Matroska container with H.264 video and AAC audio, a combination VLC and Plex handle well for a personal archive. Use it when you want one durable archive copy with room for multiple audio tracks and subtitles in the wider MKV world, not when you need to send a clip to a phone. Everything runs in your browser, never uploaded, no signup. The honest limits: the video engine loads once, about 30MB, on first use; MKV does not play natively in Safari or on some iPhones; and re-encoding can soften very low bitrate source video.

How to use this mp4 to mkv converter

From a MP4 file to a MKV file, in three steps.

1Drop in your MP4

Choose a .mp4 file from your device. The file stays in your browser and is never uploaded.

2Convert to MKV

The tool re-encodes the video and audio into the MKV combination, ready for the destination described on this page.

3Download the MKV

Save the converted file and check playback on the target player or editor before deleting the original.

Why MKV is the archive copy and MP4 is the sharing copy

Choosing MKV for this job is about the destination, not about a single best format.

An open container for long-term keeping

MKV is an open specification with broad support in VLC, Plex and desktop players, which makes it a sensible home for a copy you plan to keep for years.

Room for more than one audio track

The MKV world is designed around multiple audio tracks, subtitles and chapters, so an archive copy is not forced into the single-track simplicity of a shareable MP4.

Plays beautifully in VLC and Plex

If your library lives in VLC or Plex, MKV is a first-class citizen, with seeking and track selection that feel native rather than bolted on.

Private by design

Encoding happens on your own device, so personal footage and unreleased work never leave your browser.

MP4 to MKV Converter FAQs

Short, direct answers to the questions readers ask most.

Some loss is possible, because the video is re-encoded rather than copied frame for frame. From a high quality MP4 the difference is usually hard to notice, but the archive copy is not bit-identical to the source.

Not in general. MP4 wins for sharing and phone playback, while MKV wins for archiving and flexible libraries. Choose by the job, not by a single best-format claim.

Not natively in most cases. Use VLC on iOS or keep an MP4 copy alongside the MKV for Apple devices.

Not guaranteed. This tool converts the main video and audio track; subtitle files and chapter markers should be checked after conversion and re-added in a library tool if needed.

Yes. It runs entirely in your browser, with no account, no signup, and nothing uploaded.