MKV to MP4 is a free, in-browser video tool. Convert MKV (Matroska) to MP4 in your browser. Choose Fast (instant remux when codecs are compatible) or Re-encode (universal MP4 output) — files are processed locally with FFmpeg WASM. The page exposes a small surface — input, controls, output — so a first-time visitor can complete the job without reading documentation.
The processing pipeline is straightforward: your input is parsed by FFmpeg compiled to WebAssembly, transformed according to the options you select, and serialised back into a downloadable result. Accepted input formats are MP4, WebM, MOV, MKV, AVI, FLV, and OGV. The 500 MB per-file ceiling matches what a typical browser tab can handle without paging to disk.
The right moment to reach for MKV to MP4 is when you have a focused video editing and conversion job that fits inside a browser tab. Open the page, drop in the file or paste your input, choose the options that matter, and the tool returns the result.
Because everything runs in the page, the tool scales the same way for one user or a million — there is no per-user backend cost. The page is static, the engine is the same JavaScript bundle for every visitor, and the work happens on the visitor's own device. That keeps the tool free and keeps it fast on the first interaction.
A practical note on limits: MKV to MP4 accepts inputs up to 500 MB per run, and the tool processes one input at a time to keep memory usage predictable. If you ever bump into the ceiling, the cause is the size of the input.
MKV to MP4 is intentionally narrow in what it does, which makes it easy to slot into a longer workflow. Take its output, hand it to whichever next tool fits the job, and MKV to MP4 stays out of your way until the next time you need it.
MKV to MP4 fits naturally into the workflow of product teams shipping release demos and teams compressing demo recordings, both of whom typically need a fast result inside the browser. There is no learning curve to budget for: anyone who has used a typical web upload form can complete a run on the first try.
When the job finishes, MKV to MP4 hands you the result as `{name}-edited.{ext}`. Filenames are derived from your input where possible, so a quick batch of jobs leaves you with a tidy folder rather than a pile of generic "output (3)" files. Nothing is auto-saved on Favtoo's side because nothing was ever sent there.
MKV to MP4 is built around steady iteration on a small set of options rather than feature creep. Every additional setting attracts a slightly different audience, but a long settings panel makes the common case slower for everyone. The current controls reflect what users of the tool actually use.
From a product perspective, MKV to MP4 is one of the simplest possible expressions of "do one thing well." The catalog contains dozens of related tools that each handle a slightly different video editing and conversion task, and every one is a separate page rather than a tab inside a larger app. That separation keeps each tool fast to load and easy to bookmark.
A few practical tips that experienced users of MKV to MP4 pick up over time. First, keep your default browser updated — the engine relies on standard web APIs and newer browser versions are noticeably faster than ones from a few years ago. Second, close other heavy tabs before processing a large input; the engine shares CPU and memory with whatever else is open. Third, if you re-run the same kind of job often, your last-used settings are remembered for the rest of the tab session, so subsequent runs are essentially one click.
MKV to MP4 fits the gap where opening a desktop app feels heavy and writing a script feels overkill. The page handles the common video editing and conversion task with sensible defaults so a single visit usually completes the job; for highly specialised work, a dedicated desktop application can offer more knobs to turn.
For most failure modes, refreshing the page and re-running the job is enough — the engine has no persistent state to corrupt. If the same input fails twice in a row, the input itself is most likely the problem (a truncated file, an unexpected variant of the format, or a stream the engine does not recognise).
That is essentially everything MKV to MP4 does and how it does it. Open the tool above, drop in your input, and the work happens in the page. If you find yourself reaching for it often, bookmark the page — it loads quickly on subsequent visits, and your most-recent settings are remembered for the rest of the session.
A WebAssembly build of FFmpeg loads in this page and processes your MKV locally. Fast mode rewraps the existing video and audio streams into an MP4 container without re-encoding (instant, zero loss). Re-encode mode decodes and re-compresses with H.264 + AAC for universal playback.
Server-side tools use native multi-threaded FFmpeg with hardware acceleration. WebAssembly runs in one browser thread, typically 3–8× slower for re-encoding. Fast (remux) mode skips encoding entirely, so it finishes in seconds even for 4K files.
Try Fast first. Most MKVs already contain H.264 video and AAC audio, in which case Fast produces a perfect MP4 in seconds. If the MKV has HEVC, VP9, or unusual audio (FLAC, DTS, etc.), use Re-encode for guaranteed compatibility.
Soft subtitles inside MKV (SRT, ASS, PGS) are not preserved during conversion — MP4 has poor subtitle support. Use the Add Subtitles tool to burn them into the picture before conversion if you need them visible.
Up to 500MB. Fast (remux) mode handles even very large files easily because nothing is decoded. Re-encode mode is more memory-hungry — downscale or split first if you hit a limit.
Only the first audio track is kept. If you need a different track, pre-process the MKV to set your preferred audio as the default before converting here.
HDR10 metadata is dropped during Re-encode mode (libx264 outputs SDR). Fast mode can preserve HDR if the source codec is already H.264, but most HDR MKVs use HEVC and will be re-encoded.
No. The conversion runs entirely in your browser tab. Nothing is transmitted, stored, or logged. Closing the tab erases the file from memory immediately.
MKV to MP4 runs in any modern mobile browser — Safari, Chrome, Firefox and the in-app browsers in most messaging apps all support the underlying APIs. Performance depends on the device: a recent phone handles typical inputs nearly as fast as a laptop, while older devices may take a few seconds longer near the 500 MB ceiling. The interface lays out cleanly on small screens, so you do not need to pinch-zoom to see the controls.
MKV to MP4 accepts MP4, WebM, MOV, MKV, AVI, FLV, and OGV. If your input is in a format that is not directly supported, convert it first using one of Favtoo's converter tools — every Favtoo converter outputs a file that is a clean input to the next tool in the chain.
Failures usually fall into one of three buckets: the input is in an unsupported format, the input is over the size cap, or the input is structurally malformed (a truncated download, a partial export, or a stream the engine does not recognise). The first two are easy to confirm — check that your file is one of MP4, WebM, MOV, MKV, AVI, FLV, and OGV and that it is below 500 MB. For the third, opening the file in its native viewer first is the fastest way to confirm the source is intact.
Inputs are capped at 500 MB per file, which keeps memory usage stable across phones, tablets and older laptops. You can run MKV to MP4 as often as you need; every run produces a full-quality result.
MKV to MP4 is built on FFmpeg compiled to WebAssembly, which is the same class of engine used by professional video editing and conversion pipelines. For deterministic operations, the output is byte-identical to what an equivalent CLI run would produce; for operations involving a codec or a model, the result is well within the range of what comparable tools generate. If you have a specific reference output you need to match, run a small test job first to confirm the configuration produces what you expect.
MKV to MP4 is a static page running an open-source engine in your browser, so a typical corporate firewall does not get in the way as long as it allows JavaScript and WebAssembly to load from Favtoo. For teams that need to host it themselves on an internal network, the underlying engine (FFmpeg compiled to WebAssembly) is open-source and can be packaged into a private build with the same behaviour. Reach out via the Contact page if that is something you are exploring.
MKV to MP4 is updated whenever the underlying engine releases an improvement or a bug fix. Because the tool is delivered as a static page, every visit fetches the latest version automatically — there is no "version" to manage on your end. If a particular release ever changes default behaviour, the change is documented on Favtoo's changelog so you can confirm what shifted.
Your file is processed inside your browser by FFmpeg compiled to WebAssembly. The engine reads the file's bytes from your tab's memory, computes the result, and writes the result back into the tab. You can confirm what the page does by opening developer tools and watching the Network tab during a run — the requests you see are for the tool's static assets only.
No installation is needed. MKV to MP4 runs as a normal web page, with no browser extension, no native helper, and no separate desktop client to download. That is partly a privacy choice — extensions can request broad permissions, while a regular page is sandboxed by default — and partly a convenience one: you can use MKV to MP4 on any computer you have temporary access to without leaving anything installed on it.
Video to GIF
Convert any video clip to an animated GIF entirely in your browser. Pick the start, length, frame rate, and width — your file is processed locally with FFmpeg WebAssembly and never uploaded.
Screen Recorder
Record your screen, a window, or a browser tab directly in your browser. Optionally include system audio and your microphone. Capture, preview, and download the video without installing any app — and without uploading anything.
Webcam Recorder
Record your webcam directly in your browser with optional microphone audio. Pick the resolution (480p, 720p, or 1080p), frame rate, and mirror mode, then capture and download the result without installing any app.
Screen + Webcam Recorder
Record your screen with your webcam composited into a picture-in-picture corner — perfect for tutorials, course videos, demos, and reaction recordings. Pick the camera position, size, and audio sources, then capture and download in your browser.
Video Slideshow Maker
Turn a stack of photos into an MP4 slideshow with per-slide durations, crossfades, and an optional soundtrack. Pick the resolution (up to 1080p), frame rate, and transitions, then download a single MP4 — all processed in your browser with FFmpeg WebAssembly.
Video from Images + Audio
Combine a stack of photos with a music track or narration into a single MP4 video. Pick the resolution, per-slide duration, transitions, and let the slideshow length match the audio. All processed in your browser with FFmpeg WebAssembly.
Video Trimmer
Set precise in and out timestamps, snap to keyframes when needed, and document handles for social-safe cutdowns.
Video Splitter
Split any video into 2–10 equal-length pieces, packaged as a downloadable ZIP. Files are processed entirely in your browser with FFmpeg WebAssembly using lossless stream-copy.