Free video converter

What does a video converter do?

A video converter changes a video from one file format to another, for example MOV to MP4 or WebM to MP4, so it plays or uploads where you need it. Most “file not supported” errors are about the format, not the video itself, and converting to MP4 fixes almost all of them.

This converter runs in your browser. The video is read and written on your own device, so nothing is uploaded and there is no queue, file limit per day or watermark.

Container and codec: the two parts of a video format

A video file has two layers. The container is the box: MP4, MOV, WebM or MKV, the part you see in the file extension. Inside it are streams compressed with a codec, such as H.264 or HEVC for video and AAC or Opus for audio.

That is why two MP4 files can behave differently: one holds H.264 and plays everywhere, the other holds a codec your player doesn’t know. And it is why some conversions are almost instant while others take longer:

• Copy (remux). When the streams inside already play well in the new container, they are moved into it unchanged: H.264 from a MOV into an MP4, for example. It is fast and loses nothing, and the tool tells you before you start.
• Re-encode. When they don’t, the video is decoded and compressed again: H.264 with AAC for MP4, MOV and MKV, VP9 with Opus for WebM. You choose smaller file, balanced or high quality, and can lower the resolution at the same time. It takes longer, and like any re-encode it loses a little detail.

Which format should you choose?

If you only remember one thing: convert to MP4 unless something specifically asks for another format. It opens in browsers, on iPhone and Android, in Slack, Teams and email previews, and in nearly every video editor and learning platform.

How to fix “file format not supported”

1. Check what the file really is. A video metadata viewer shows the container and the codecs, so you know whether the problem is the box or what’s inside.
2. Convert it to MP4 here. That fixes the container. H.264 and HEVC video is copied as it is; if the player can’t handle HEVC, also choose a lower resolution, which re-encodes the video to H.264.
3. If the site has a size limit as well, run the result through the video compressor.

Common conversions

• MOV to MP4: iPhone videos and Mac screen recordings for Windows, Android and the web.
• WebM to MP4: recordings from browser-based screen recorders.
• MKV to MP4: OBS recordings ready to share or edit.
• MP4 to WebM and MP4 to MOV: for websites and Apple workflows.
• MP4 to MP3: just the sound, for voice-overs, podcasts and transcripts.

What it can’t convert

The converter can only work with codecs your browser can decode. That covers H.264, HEVC on most current Macs and PCs, VP8, VP9 and AV1, and the usual audio codecs. Professional formats such as Apple ProRes and older containers such as AVI and WMV aren’t supported; for those, use a desktop app. If your browser can’t decode or encode a video, the tool tells you so instead of producing a broken file.

Tips for a clean conversion

Convert from the original

Each re-encode loses a little detail. Convert the file you recorded, not a copy that was already converted or compressed.

Keep the tab open

Your computer does the work, so speed depends on your device and the length of the video. Short clips take seconds; a long recording on an older laptop can take a few minutes.

Check the sound

If the browser can’t process the audio of a file, the tool tells you, and the result has no sound. Converting from the original recording usually avoids that.