Video to MP3 Converter

How to convert a video to MP3

1. Drag a file onto the drop zone, or press Choose file and select one. Video files (MP4, MOV, WebM) and audio files (M4A, WAV, OGG and similar) are accepted.
2. Before you start, pick a quality: 128, 192 (the default), 256 or 320 kbps. The setting is read at the moment you add the file.
3. Watch the status line: it moves from reading, to decoding, to a percentage while encoding.
4. When it says "Done", a new row appears with the file name, its size in MB and a Download MP3 button. The new file keeps the original name with the extension changed to .mp3.

Only one file is converted at a time, and if you drop several files, only the first is used. Finished files stay in the list for the current visit, newest at the top, so you can convert a few in a row and download them afterwards.

What happens inside your browser

There are three steps. First, your browser's own decoder reads the audio track out of the file. Second, the samples are converted to 16-bit integers. Third, an MP3 encoder (the open-source LAME encoder compiled to JavaScript) compresses them in blocks of 1,152 samples, which is the size of one MP3 frame. The work is split into small chunks so the page stays responsive and the percentage can update.

The audio is kept in stereo if the source has two or more channels (only the first two are used) and in mono if the source is mono. The sample rate follows what the browser decoded, so you do not choose it. No part of the file is uploaded, which also means you can use it offline after the page has loaded.

Choosing a bitrate and estimating file size

MP3 at a constant bitrate has a simple size rule: kilobits per second divided by eight gives kilobytes per second. One minute at 192 kbps is about 1.4 MB; ten minutes is about 14 MB. The same ten minutes would be roughly 9.6 MB at 128 kbps and 24 MB at 320 kbps.

• 128 kbps: fine for speech, podcasts and lectures, and the smallest file.
• 192 kbps: a sensible default for most music and mixed content.
• 256 and 320 kbps: larger files with a smaller quality loss; useful if the source is itself high quality and you plan to listen on good equipment.

Keep in mind that a higher bitrate cannot restore detail that the original already lost. If your source is a low-bitrate video soundtrack, 320 kbps only makes a bigger file, not a better one. MP3 is a lossy format, so converting an already compressed track adds a second round of compression; keep the original if you may need it later.

Common uses

• Saving the audio of a lecture, interview or meeting recording to listen to on a phone.
• Extracting a voice-over or music bed from your own video project.
• Reducing a heavy WAV recording into a file small enough to send by email.
• Making an audio-only copy of a family video for a device that cannot play video.

Troubleshooting and limits

• "Could not decode": the browser has no decoder for that audio format, or the file has no audio track at all. A screen recording made without sound is an example of the second case.
• Memory: the whole file is read into memory and decoded to raw samples, which are much bigger than the original audio. One hour of stereo audio is roughly 600 MB of raw data before encoding, so very long files can fail on phones and older computers. Splitting the video first helps.
• Encoding speed: it runs on your own processor, so a long file takes a while. Keep the tab open until it finishes.
• Multichannel audio: 5.1 surround sources are reduced to their first two channels rather than mixed down, so the result may sound different from the original.
• No tags or chapters: the output has no title, artist or cover image information.

Respect copyright. Convert only recordings you made or have permission to use.

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