Convert MP4 to MP3 Online
Pick an MP4 file from your device and extract the audio as a high-quality MP3. Free, with no monthly limit, and it runs entirely in your browser.
How it works
- Upload your MP4 video. Drag your MP4 file into DomeScribe or click to browse. Large files are limited by your device's memory — up to about 500 MB works reliably.
- Keep MP3 as the output. MP3 is selected by default and free. It is encoded at the encoder's highest variable-bitrate quality setting (roughly 220–260 kbps); paid plans add M4A, FLAC, WAV, and a straight copy of the original AAC stream.
- Extract the audio. Click Extract. DomeScribe drops the video stream and encodes the audio to MP3 on your device — nothing is uploaded. A short clip takes seconds; an hour-long recording a few minutes.
- Save the MP3. Save the resulting file to your device (free account). It plays in any music app, phone, or car stereo.
Converter at a glance
- Video formats
- MP4, MOV, AVI, WebM, MKV, FLV — optional resolution (4K to 360p) and frame rate (60/30/24 fps)
- Audio formats
- MP3, WAV, FLAC, AAC, OGG, M4A
- Privacy
- Runs 100% in your browser (WebAssembly) — your file is never uploaded to a server
- Speed
- No upload wait — processing starts as soon as the in-browser engine loads (~31 MB, cached after the first run)
- File size
- Limited by your device's memory — up to about 500 MB works reliably
- Watermark
- None
- Limits
- Free — no monthly limit; runs on your device (a free account is needed to save the file)
Frequently asked questions
Does converting MP4 to MP3 affect audio quality?
The MP3 is encoded at the encoder's highest variable-bitrate quality setting (roughly 220–260 kbps on average). If the MP4's AAC track was itself high quality, most listeners will not hear a difference. For zero loss, paid plans can copy the original AAC stream out as M4A.
How much smaller will the MP3 be compared to the MP4?
Dramatically smaller, because the video data — the vast majority of an MP4 — is discarded entirely. A 500 MB music video typically produces an MP3 of around 10 MB, depending on song length.
Can I extract audio from a long MP4 recording like a lecture or podcast?
Yes, as long as the file fits in your device's memory — up to about 500 MB works reliably. Long recordings such as lectures or webinars extract fine; the resulting MP3 is ideal for offline listening.
Can I choose the MP3 bitrate?
Not in the extractor — it always uses the highest variable-bitrate setting. If you need a smaller file at a specific bitrate (64, 128, 192, or 320 kbps), run the MP3 through DomeScribe's in-browser audio compressor afterwards.
Is the MP4 uploaded anywhere?
No. The MP4 is read and the audio encoded entirely in your browser. Nothing is sent to a server, and there is no monthly limit on how many files you convert.
Related tools
- Free Online Video & Audio Converter — Convert video and audio files between formats in your browser — MP4, WebM, MOV, MKV, AVI, MP3, FLAC, WAV and more. Free, no monthly limit, nothing is uploaded.
- Extract Audio from Video — Extract the audio from a video file on your device as MP3 — free, no monthly limit. Runs in your browser, nothing is uploaded. FLAC, WAV, M4A on paid plans.
- Convert Video to Audio Online — Convert a video file to audio free, in your browser. Extract the audio track as MP3 (FLAC, WAV, M4A on paid plans) — nothing is uploaded, no monthly limit.