Audio / Formats
MP4 to MP3 Converter
Save an MP4 video's soundtrack as an MP3 for listening without the picture. Preview the first eight seconds at your chosen bitrate before converting the whole track.
MP4 to MP3 Converter: Create an audio-only listening copy of a local MP4 video, such as a recorded presentation with a readable soundtrack. The converter discards the picture and re-encodes the decoded audio as MP3. Listen to the first eight seconds at the chosen bitrate before converting the full track; that sample may not reveal a problem later in the recording. Runs 100% locally in your browser with zero server file uploads.
- Category
- Video tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
Files stay on this device. MP3 is lossy; converting cannot restore detail. Protected or unsupported audio cannot be converted.
MP3 encoding uses LAME under the LGPL, loaded from this site as a separate file. LAME source and licence
Estimating the audio-only download
For duration t in seconds and constant MP3 bitrate b in kbit/s, approximate encoded audio bytes = t × b × 1,000 / 8. This is an estimate because frame padding and encoder delay affect the actual file. Video resolution does not appear in this formula: the picture is discarded, so soundtrack duration and the selected bitrate drive MP3 size. Worked example: a 60-second presentation at the default 192 kbit/s gives 60 × 192 × 1,000 / 8 = 1,440,000 bytes, or 1.44 decimal MB before small framing differences. For a 60-second stereo example at 44.1 kHz, the complete encoded download is 1,440,705 bytes including framing, close to the estimate. The finished download displays its measured size. The eight-second preview alone is not the full minute.
Container support and the listening workflow
The Library of Congress MPEG-4 description (https://www.loc.gov/preservation/digital/formats/fdd/fdd000155.shtml) explains how an MP4 container holds media tracks. Its filename extension does not guarantee that every browser can decode the particular audio coding inside. Choose an unprotected local file; the tool does not accept a streaming URL. The W3C Web Audio specification (https://www.w3.org/TR/webaudio-1.1/) describes decoding and resampling browser audio. This converter uses 44.1 kHz decoded audio and retains stereo unless mono is selected. For a lecture, check that both speakers remain audible after any mixdown. Keep the original video if you need visual context or want to make another format later.
How to use it
- Choose an unprotected MP4 file with a readable audio track.
- Choose MP3 bitrate and whether to mix down to mono; listen to the live sample.
- Convert the full audio and download the MP3.
Privacy & limitations
Files stay on this device. A bundled MP3 encoder loads from this site when needed. Protected files and codecs the browser cannot decode are unsupported; the input limit is 250 MB.
Related tools
Frequently asked questions
What happens to captions and the picture?
The downloaded MP3 contains audio, not the video frames or a rendered subtitle track. If important information is only shown on screen, an audio-only copy will omit it. Keep the original presentation for diagrams and other visual material.
Can I convert a silent MP4 or choose another soundtrack?
A readable audio track is required. A video with no audio track cannot provide sound to encode. This interface does not offer an alternate-language or track selector; check that the decoded preview contains the soundtrack you need.
Will a higher MP3 bitrate restore sound damaged in the video?
No. Re-encoding can introduce further loss, and a higher bitrate cannot recover missing detail. Use the preview to check speech clarity, then listen to the full output, especially if the useful audio begins after the short sample.
Free tool · runs in your browser · no account required