Video Converter
Upload a video to convert or drag and drop
MP4, MOV, WebM, MKV and more. Everything happens in your browser - nothing is uploaded.
Runs entirely in your browser using ffmpeg compiled to WebAssembly. Your video is never uploaded. Re-encoding is heavy work done on your own device, so long videos take time and are best converted on a desktop.
Turn a video into the format you actually need. Upload an MP4, MOV, WebM, or MKV, choose the output format, and download the converted file. MP4 with H.264 plays almost everywhere, WebM is a small open format for the web, and MOV and MKV suit Apple software and flexible containers. It re-encodes with sensible, widely-compatible settings, and changes the container without re-encoding when it can. Everything runs in your browser with ffmpeg compiled to WebAssembly, so the video is never uploaded.
How to use this tool
- 1Upload a video (MP4, MOV, WebM, MKV, and more).
- 2Choose the format to convert to: MP4, WebM, MOV, or MKV.
- 3Read the short note under the format to check it fits your use.
- 4Click Convert, and wait - re-encoding takes longer on long videos.
- 5Download the converted file when it is ready.
Example
Upload a .mov straight from an iPhone, choose MP4, and convert. You get an H.264 MP4 with fast-start enabled, which uploads cleanly to sites and plays on Windows, Android, and the web without extra software.
Upload an MP4, choose WebM (VP9), and convert. The result is an open-format file that is often smaller at the same quality, ideal for embedding on a website. VP9 encoding is slower, so allow more time for longer clips.
Common use cases
- Converting an iPhone MOV to MP4 so it plays on any device or website
- Turning an MP4 into WebM for a smaller, web-friendly upload
- Getting an MKV download into MP4 so a phone or TV can play it
- Producing a MOV for a video editor that prefers QuickTime files
- Standardising a folder of mixed clips into one common format
Common mistakes
- Converting to the same format you started with - that re-encodes and can lose quality for no gain; the tool warns you when the input already matches the target.
- Expecting WebM to be instant - VP9 encoding is slower than H.264, so a WebM export takes noticeably longer.
- Converting a very long video on a phone - re-encoding is heavy and uses a lot of memory; use a desktop for large files.
- Assuming MKV or MOV changes the video itself - when the codecs already fit, only the container changes, so the picture is identical.
Frequently asked questions
Is my video uploaded anywhere?
No. Conversion runs entirely in your browser using ffmpeg compiled to WebAssembly. The video never leaves your device, which makes it safe for private or unreleased footage.
Which format should I choose?
MP4 (H.264) is the safe default and plays on almost anything. WebM is a small, open format best for websites. MOV suits Apple software and editors, and MKV is a flexible container. If you are unsure, choose MP4.
What is the difference between a format and a codec?
The format, or container, is the file type such as MP4 or MKV; the codec is how the video inside is encoded, such as H.264 or VP9. This tool outputs H.264 in MP4, MOV, and MKV, and VP9 in WebM, which are the most compatible choices.
Will converting change the file size?
Often yes. Re-encoding to a different codec can make the file larger or smaller depending on the format and quality. The tool shows the original and converted sizes so you can compare. To target a smaller size specifically, use the Video Compressor.
Why is it slow on a big video?
Re-encoding runs on your own device rather than a server, and WebM in particular is slow. Longer and higher-resolution videos take more time and memory, so large files are best converted on a desktop rather than a phone.
Does it keep the audio?
Yes. The audio is converted along with the video - to AAC for MP4, MOV, and MKV, and to Opus for WebM - so the converted file still has sound.
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