MP4 to MP3: how to get the audio out of a video
Turn an MP4 into an MP3 in your browser: which bitrate to pick, how big the file gets, album cover art, iPhone and Android steps, and common fixes.
Updated
Short answer: to turn an MP4 into an MP3, open an MP4 to MP3 converter, drop the video in, pick a bitrate (192 kbps is right for almost everything) and download the MP3. On Nibbo’s MP4 to MP3 page this happens inside your browser, so it’s free, there’s no daily limit and the video is never uploaded. Only the sound is kept. The picture is thrown away.
How to convert MP4 to MP3 on Nibbo
- Open MP4 to MP3.
- Drop your video onto the Drop MP4 files box, or click it to choose files. You can add several at once, and MOV, MKV, WebM and 3GP videos work too.
- Under Save as, check that MP3 is selected. The page remembers your last choice, so if you used another format before, switch it back.
- Pick a Quality: 320, 256, 192 (the default), 128 or 64 kbps, or VBR V0 / V2. Leave Channels on As source, or choose Mono for a talk.
- Click Convert to MP3 (with several files: Convert 3 files to MP3). The first time, the LAME MP3 encoder downloads once (130 KB).
- Each file shows its length, the original size and the MP3 size, plus a player to check it. Click Download, or Download all (ZIP) when you converted more than one.
Files are converted one after another, so you can queue a whole folder of recordings and leave it running.
Which bitrate to choose
MP3 is lossy: the encoder throws away sound you are unlikely to hear, and the bitrate says how much data is left per second.
| Quality | Good for | Size per minute |
|---|---|---|
| 320 kbps | When a site or a DJ asks for “320” | about 2.4 MB |
| 192 kbps (default) | Music, concerts, anything you’ll listen to | about 1.4 MB |
| 128 kbps | Music on phone speakers, background listening | about 1 MB |
| 64 kbps (voice) | Lectures, meetings, sermons, podcasts | about 0.5 MB |
| VBR V0 / V2 | Music, spending bits only where the sound needs them | varies, around 245 / 190 kbps |
The math is simple: kilobits per second ÷ 8 × seconds. A one-hour lecture at 64 kbps is about 29 MB; the same hour at 192 kbps is about 86 MB.
Higher doesn’t always mean better. The audio in an MP4 is usually already compressed, almost always as AAC. Converting it to MP3 is a second lossy step, and the MP3 can never sound better than the AAC it came from. A 320 kbps MP3 from a phone video takes more space than a 192 kbps one, but won’t sound any better.
What you keep and what you lose
- Kept: the full soundtrack at its original sample rate. A 44.1 kHz track stays 44.1 kHz, a 48 kHz phone recording stays 48 kHz. Nothing is resampled behind your back.
- Surround sound (5.1) is mixed down to stereo, because MP3 holds at most two channels.
- Only the first audio track is converted. If a video has several languages, you get the default one.
- The picture is gone, and so is everything stored alongside it.
MP4 to MP3 with album cover
Nibbo writes a plain MP3 with no tags: no title, no artist and no cover art. Nothing from the MP4 is copied over, not even a thumbnail. Phone videos and screen recordings don’t have a cover to begin with.
If you want artwork in your music app, add it after converting:
- Mac: in the Music app, add the MP3 to your library, then choose Song → Info → Artwork → Add Artwork.
- Any computer, with FFmpeg:
ffmpeg -i song.mp3 -i cover.jpg -map 0 -map 1 -c copy -id3v2_version 3 -metadata:s:v comment="Cover (front)" song-with-cover.mp3 - Any ID3 tag editor can do the same, on Windows, Android or iPhone.
A square JPEG of around 1000 × 1000 pixels is plenty. To make one from a still of the video, take a screenshot and use Crop image with the 1:1 ratio.
On iPhone, Android, Windows and Mac
iPhone and iPad (Safari): tap the drop box and choose Photo Library for a video you shot, or Choose File for one in the Files app. The MP3 goes to Files → Downloads. Long videos need a lot of memory, so close other apps first.
Android (Chrome): tap the box, pick the video from the gallery or the file manager. The MP3 lands in Downloads.
Windows and Mac: drag one or many videos from File Explorer or Finder straight onto the box. A computer is the best choice for recordings longer than an hour or two.
Common errors and fixes
- The file says Failed with “No audio track found in this file”. The video really has no sound. This is common with screen recordings made without the microphone on, and with silent clips.
- “The audio engine ran out of memory.” The whole soundtrack is decoded into memory before it’s encoded, and an hour of stereo audio needs roughly 1.4 GB. Try on a computer, close other tabs, or split the recording first.
- It shows “Loading the universal decoder…”. That’s normal for videos over 512 MB or for formats the browser can’t open on its own. FFmpeg loads once and reads the file without copying it into memory first.
- M4A or Opus is greyed out. Those use your browser’s own encoder, and some browsers don’t have one. MP3 works in every browser.
- A film bought in a store won’t convert. Copy-protected (DRM) videos can’t be decoded by a browser.
Is it really free and unlimited?
Yes. There are no daily limits, no queue, no account and no watermark: the work runs on your device, so there’s no server time to ration. The site handles files up to 3 GB, and for MP4 to MP3 what really matters is how long the audio is and how much memory your device has. Once the page and the encoder have loaded, it keeps working offline.
FAQ
Is my video uploaded?
No. The video is decoded and the MP3 is encoded in your browser tab. You can check with the airplane-mode test.
Can I convert only part of the video?
Use Cut audio: drop the MP4, drag the handles on the waveform, add a fade if you like and save the selection as MP3.
What about M4A, WAV or other formats?
The audio converter takes the same videos and saves MP3, M4A, Opus, OGG, FLAC or WAV. iPhone voice memos are M4A, and M4A to MP3 is set up for them.