Free MP4 to MP3 Converter
Extract the soundtrack from MP4, MOV, WebM or MKV video and save it as MP3 at 128, 192, 256 or 320 kbps. Converted locally, no uploads or signup.
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How to convert MP4 to MP3 without uploading the video
Use this converter when you have a video and only need its sound: a recorded lecture, an interview, a music performance or a screen recording with narration. For audio files that are already audio, the Audio Converter is the right tool, and Remove Audio from Video does the opposite job by keeping the picture and dropping the sound.
- Choose or drop a video file up to 200 MB. MP4, MOV, WebM, MKV, M4V and AVI are accepted.
- Pick a bitrate: 128 kbps for speech, 192 kbps as a good all-round choice, or 256 to 320 kbps for music.
- Optionally change the channels to mono for spoken word, and keep 44.1 kHz for the widest player compatibility.
- Select Extract MP3. The processing engine downloads once (about 31 MB) and the progress bar shows the conversion.
- Preview the MP3 in the player, then choose Download MP3.
When to extract MP3 audio from a video
Many recordings start life as video even though only the sound matters. A university lecture recorded on a phone, a webinar you downloaded, a podcast that was filmed for a video platform, a family member’s voice from an old clip, or a rehearsal you want to listen to while commuting are all easier to use as MP3. An MP3 is far smaller than the video and plays on almost every device, car stereo and app.
Choose this tool when your input is a video file. If you already have audio, such as WAV, M4A or FLAC, the Audio Converter handles audio-to-audio conversion with more output formats. If you want the opposite, a silent video, use Remove Audio from Video. To shorten a clip first, cut it with the Video Trimmer and then extract the audio.
Worked example: a song and a lecture
MP3 at a constant bitrate uses the bitrate multiplied by the duration. A 4-minute music video is 240 seconds. At 192 kbps the MP3 is 240 × 192,000 ÷ 8 = 5,760,000 bytes, about 5.8 MB. At 128 kbps it would be 3,840,000 bytes (3.8 MB) and at 320 kbps 9,600,000 bytes (9.6 MB). The source video might be 60 MB or more, so the audio is a small fraction of it.
A 45-minute lecture is 2,700 seconds. At 128 kbps mono it becomes about 43,200,000 bytes, roughly 43 MB, which is a sensible size for spoken word. At 192 kbps it would be 64.8 MB with no audible benefit for a voice recorded on a phone. The tool shows this estimate as soon as it can read the video’s duration, so you can choose before converting.
How the conversion works
The converter uses FFmpeg compiled to WebAssembly, the same self-hosted engine as the site’s Audio Converter. The first time you convert, your browser downloads the engine files from this site, about 31 MB, and checks a SHA-256 fingerprint before running it. After that the browser usually serves it from its cache.
Your video is read into the tab’s memory and handed to the engine in a background worker so the page stays responsive. For a 128 kbps mono job the engine runs the equivalent of: -i input.mp4 -map 0:a:0 -vn -map_metadata -1 -c:a libmp3lame -b:a 128k -ac 1 -ar 44100 output.mp3. In plain terms, it takes the first audio track, ignores video and subtitles, removes metadata, and encodes MP3 with the LAME encoder at the chosen bitrate. The finished file is passed back to the page for preview and download.
Common mistakes to avoid
Picking 320 kbps to “improve” quality is a frequent misunderstanding. The video’s audio is already compressed, often as AAC, and re-encoding it to MP3 can only keep or lose detail, never add it. Choose a bitrate at or slightly above the source and save space.
Very large or very long videos can exceed the memory a browser tab may use, especially on phones. If a conversion fails with a memory message, trim the video first or try on a computer. Also check that you have the right to use the audio; extracting sound from a video does not change who owns it.
Useful tips and limitations
- A higher bitrate cannot add quality that the video’s own audio track never had. Phone and camera videos usually already carry compressed AAC audio.
- Only the first audio track is extracted. If a film has several language tracks, convert a copy where the language you want is first.
- Use mono for interviews and lectures recorded on a single microphone; the file is the same size at a given bitrate but can sound cleaner at lower bitrates.
- Keep 44.1 kHz unless you are going to edit alongside other 48 kHz video audio, in which case choose 48 kHz to avoid an extra resample later.
Common questions
Is my video uploaded to a server?
No. The video is read into this browser tab and converted with a copy of FFmpeg compiled to WebAssembly that is served from this site. Nothing is sent to ToolWorld Online.
What happens if my video has no sound?
The converter tells you the file has no audio track. Screen recordings made without a microphone and some GIF-style clips have no sound to extract.
Which bitrate should I pick?
Use 128 kbps for lectures and podcasts, 192 kbps for general listening and 256 or 320 kbps for music you care about. The estimated file size updates as you change the setting.
Does this convert WebM and MKV as well as MP4?
Yes. MP4, MOV, WebM, MKV, M4V, AVI, 3GP, MPEG and WMV are accepted, provided the browser engine can decode the audio codec inside. Most AAC, MP3, Opus and Vorbis tracks work.
How large an MP4 can I convert to MP3?
Videos up to 200 MB are accepted so that the conversion fits in the memory available to a browser tab.
Can I convert several videos at once?
Convert them one after another. The engine stays loaded between conversions, so the second file starts much faster than the first.
Your video is processed locally in this browser with a self-hosted FFmpeg engine. It is never uploaded to ToolWorld Online. Save the MP3 before closing the page.