Video Converter

What this tool is for

A video shot on one device or exported from one piece of software often doesn't play, edit, or upload cleanly somewhere else. A phone might record in a codec a video editor doesn't recognise; a screen recording tool might save AVI when a web platform only accepts MP4; an old MKV file might refuse to play in a browser tab at all. This tool changes the container and codec of a video file so it works where you actually need it, without installing desktop software or sending the file to a server first.

It's aimed at anyone who has a video in the wrong format for what they're trying to do next: uploading to a website that's picky about file types, opening a clip in an editor that doesn't support the source codec, or simply wanting a smaller, more universally-playable MP4 instead of a niche format. If your actual goal is a smaller file rather than a different format, use the Video Compressor instead — changing the container alone rarely reduces file size by much, since the video data itself is mostly untouched.

How the video converter actually works

This tool runs ffmpeg.wasm, a WebAssembly build of the real ffmpeg project, directly in your browser tab — not a lookalike or a simplified reimplementation, the same decoder and encoder library used by desktop video software. When you convert a file, the tool hands ffmpeg a single command: read the input file and write it out under the new extension, letting ffmpeg choose the standard codec for that container (for example, H.264 video with AAC audio for an MP4 target). There's no separate quality or bitrate control on this page by design — that's what the Video Compressor's CRF slider is for. This tool answers one question only: same content, different format.

The trade-off worth understanding is that this is a genuine re-encode, not a fast "remux" that just repackages existing data into a new container. Re-encoding means decoding every frame and encoding it again, which is why longer or higher-resolution clips take proportionally longer and why a very old or low-powered device will feel it. It also means there is a small, usually invisible quality cost inherent to any re-encode — converting and converting back is never byte-identical to the original, the same way it wouldn't be with desktop software.

When MP4, WebM, AVI, or MKV actually matters

MP4 is the safest default: it plays natively in essentially every browser, phone, and video platform, and is the right choice if you're not sure what you need. WebM is worth choosing specifically for web use — it's an open format built for browser playback and tends to produce smaller files at comparable quality for web delivery, though it has weaker support in some older desktop players and non-browser software. AVI is an older container mostly relevant if a specific older program or device requires it; there's rarely a reason to convert to AVI for a modern workflow. MKV is the most flexible container and a good target if you need to preserve multiple audio tracks or subtitle streams, but it has the least universal playback support of the four, particularly on mobile and in-browser.

Common situations this solves

• A screen recording won't upload. Many screen-capture tools default to formats a video platform doesn't accept — converting to MP4 usually resolves this immediately.
• A phone video won't open in an editor. Some editing software doesn't support every phone codec; converting to MP4 or MKV first is often the quickest fix.
• An old MKV or AVI file won't play in a browser tab. Converting to MP4 makes it playable directly in nearly any browser without a separate media player.
• You need multiple audio tracks preserved. Converting to MKV keeps multi-track audio and subtitle streams that MP4 handles less flexibly.

Limitations, honestly

This is a real re-encode running on your own CPU, so speed depends entirely on your device — a modern laptop handles a few minutes of HD video quickly, while an older phone or a very long or high-resolution file can take substantially longer, or run into memory limits in the browser tab. There is no hard file-size cap, but very large files (multi-gigabyte 4K footage in particular) are the most likely to struggle on lower-powered hardware. The tool also does not let you choose a specific codec or bitrate within a container; if you need fine control over output quality, use the Video Compressor's CRF setting after converting.

Frequently asked questions

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