MP4 to MP3 Converter
Turn the sound of any video into an MP3, with tags and cover art, on your own device.
Details from the file
Files
Preview
Play or drag to a moment, then use it as the cover picture or as the start or end of the MP3 (under Trim and fade).
MP3 settings
Trim and fade (optional) Whole file · no fades
Type minutes and seconds such as 1:23.5, or seconds such as 83.5. Fades are linear and shortened to half the length if the result is short.
What you will get
Output
Working…
Your MP3
Change the settings above and run it again to try another version; the original stays open.
About the MP4 to MP3 Converter
Take the soundtrack out of an MP4, MOV, MKV, WebM, M4V or 3GP video and save it as an MP3 that plays on every phone, car stereo and music app. Choose a constant bitrate from 64 to 320 kbps, or LAME’s variable bitrate levels, which spend more bits on busy passages and fewer on quiet ones.
You can trim the MP3 to part of the video and fade it in and out, fill in the ID3 tags (title, artist, album, year and more) and give it cover art — a frame of the video you pick in the preview, or any picture. If a video has several sound tracks (languages, commentary), you choose which one. Several videos can be converted in one go and downloaded as a ZIP.
Everything runs in your browser: the video is read from your device, decoded, and encoded with LAME, and nothing is uploaded.
How to use it
- Drop a video on the box or press Choose videos. To convert several at once, choose them together.
- Check the Sound line (pick a track if the video has more than one) and set the bitrate: constant (CBR) or variable (VBR), plus the sample rate and channels if you need to.
- Optionally open Trim and fade to keep only part of the video, and fill in the tags. For cover art, play or drag the preview to a good moment and press Use the frame shown in the preview.
- Press Convert to MP3, listen to the result, and press Download.
Examples
concert.mp4 · AAC 48 kHz stereo, 128 kbps
concert.mp3 · 192 kbps CBR · 48 kHz stereo, title “concert”, a frame of the stage as square cover art
48 kHz is a valid MP3 rate, so the sound is not resampled.
lecture.mkv · track 1 English (AAC), track 2 Hindi (Opus)
lecture.mp3 from track 2 · VBR -V 5 · mono
trailer.mkv · Dolby Digital (AC-3) 5.1
trailer.mp3 · stereo, with the centre and surrounds mixed in at −3 dB (ITU-R BS.775)
Trim 1:12.0 to 1:46.5 · fade in 1 s · fade out 3 s
A 34.5-second MP3 that starts and ends softly
CBR or VBR, and which bitrate?
- Constant bitrate (CBR) uses the same number of bits every second. 128 kbps is fine for speech, 192–256 kbps is a common choice for music, and 320 kbps is the highest MP3 allows (ISO/IEC 11172-3). Every player shows the exact length and seeks precisely.
- Variable bitrate (VBR) lets LAME choose the bits per frame to keep the quality level you pick. Typical averages on music, as commonly published for LAME, are -V 0 about 245 kbps (LAME’s “extreme” preset), -V 2 about 190 kbps (“standard”), -V 3 about 175, -V 4 about 165 (“medium”) and -V 5 about 130 kbps; LAME’s own usage notes put -V 2 at about 200 and -V 5 at about 132 kbps. Speech and quiet recordings come out smaller; the finished file shows its real average. The page writes a Xing header so players can show the length and seek.
The soundtrack of most videos is already compressed (usually AAC), so converting it to MP3 is a second lossy step. At 192 kbps or -V 2 and above that is very hard to hear; a higher bitrate than the original’s makes the file larger without improving it, and the page says so. If you want the original sound untouched, use Extract Audio from Video, which copies it without re-encoding.
Sample rate and channels
Video soundtracks are usually 48 kHz, which MP3 can store, so by default nothing is resampled. You can choose 44.1 kHz (the CD rate), or a lower rate such as 22.05 kHz with mono for speech to make the file much smaller; the page then resamples with a band-limited (windowed-sinc) filter, so no false tones fold back into the audible range. Rates MP3 cannot store (such as 96 kHz) become 48 kHz.
MP3 holds one or two channels. Surround sound (5.1, 7.1) is mixed down to stereo with the ITU-R BS.775 coefficients — centre and surround channels at −3 dB, the LFE channel left out — and scaled so it cannot clip. Mono mixes left and right; left only or right only keeps one side, useful when a microphone was recorded on one channel.
Tags and cover art
The MP3 gets ID3v2.4 tags: title (TIT2), artist (TPE1), album (TALB), year or date (TDRC), track (TRCK), genre (TCON), album artist (TPE2), disc (TPOS), composer (TCOM), copyright (TCOP) and a comment (COMM). The title starts as the video’s own title tag, or its file name.
Cover art is stored as an attached picture (APIC, front cover). Pick a frame in the preview and press Use the frame shown in the preview; tick Crop to a square for players that show covers as squares. Large pictures are saved as a JPEG of at most 1000 pixels so the MP3 does not grow needlessly.
Limitations
- Old video formats — AVI, WMV/ASF, FLV, MPG/VOB, RealMedia — cannot be read in a browser; the page says so when you choose one. Convert them to MP4 with a desktop tool first.
- Videos protected by DRM (for example downloads inside streaming apps) cannot be opened.
- Decoding AAC and Opus sound needs WebCodecs (a current Chrome, Edge, Firefox or Safari); Dolby Digital and DTS are decoded with WebAssembly.
- A frame can only be taken from video the browser can decode; HEVC (H.265) video, for example, depends on the device. You can still choose an image file as the cover.
- Long videos take a while on phones, and the finished MP3 is kept in memory until you download it.
- Trimming in a batch is not offered: each file is converted whole with the same settings.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot. The audio engine and the LAME MP3 encoder download from MySmartCoPilot the first time you use them (about 2.4 MB more for variable bitrate). Your videos are never uploaded.
Frequently asked questions
Is the MP3 lower quality than the video’s sound?
Slightly, because the sound is decoded and encoded again. At 192 kbps CBR or VBR -V 2 and above the difference is very hard to hear. To keep the original sound exactly, use Extract Audio from Video, which copies the track without re-encoding (usually as .m4a).
Which bitrate should I choose?
128 kbps for speech and podcasts, 192–256 kbps for music, 320 kbps if you want the highest MP3 quality. VBR -V 2 (about 190 kbps on typical music) is LAME’s “standard” preset and usually gives a smaller file than 256 kbps CBR at a similar quality.
How do I use a frame of the video as album art?
Play or drag the preview to the moment you want, then press Use the frame shown in the preview under Cover art. Tick Crop to a square if you want a square cover, and check the picture before converting.
Can I convert only part of a video?
Yes. Open Trim and fade, type a start and an end time (like 1:12.5), or press the buttons to take them from the preview’s position, and add a fade in or out if you like.
The video has two languages. Which one is converted?
The first sound track the browser can decode, unless you choose another under Sound track to convert in the file panel.
Can I convert several videos at once?
Yes. Choose them together: they are converted one after another with the same MP3 settings, each keeps its own title (or file name), and you can download them one by one or as a ZIP.
Is my video uploaded?
No. The video is read and converted in your browser; only the converter’s code is downloaded from MySmartCoPilot the first time.