MP4 to MP3 Converter

Convert the audio without handing over the video

The file selector gives this browser access only to the MP4 you choose. The page reads the container and audio track locally, creates an MP3 locally, and exposes the result as a temporary browser download. Reloading or closing the page clears that temporary result.

This is narrower than a server converter by design. The page checks the actual MP4 structure and asks the browser whether it can decode the audio track. Unsupported codecs stay unsupported rather than being uploaded behind a vague privacy promise.

Choose settings that match the job

For spoken notes, lectures or interviews, 64–128 kbps and mono can reduce the output size. For music, start at 192 kbps stereo and compare the preview with the source. A larger bitrate stores more MP3 data, but it cannot recover quality that the MP4 never contained.

The size shown before conversion is an estimate based on duration and selected constant bitrate. MP3 headers and encoder behavior can make the downloaded file slightly different, so the finished result shows its measured size.

Trim before the browser does the work

Use seconds for the start and end. Leaving the full detected range keeps the whole audio track; shortening the range encodes only that section. The end must be after the start and cannot exceed the detected audio duration.

Conversion speed depends on the clip length, codec, browser and device. Keep the page open while it runs. If a phone becomes warm or memory is tight, cancel the job and try a shorter range. ToolNeko does not claim a guaranteed speed or universal MP4 support.