Which format to choose
| Format | Best for | Size |
|---|---|---|
| MP3 | Playing anywhere: phones, car stereos, speakers, websites | About 1.4 MB a minute at 192 kbps |
| M4A (AAC) | iPhone, Apple Music, and better sound than MP3 at the same size | Same as MP3 at the same bit rate |
| WAV (16-bit PCM) | Editing software, some upload forms and transcription services | About 10 MB a minute, uncompressed |
| OGG (Vorbis) | Games, websites, Android | Similar to MP3 |
| FLAC | Archiving music without any loss | Often about half the size of WAV |
For MP3, M4A and OGG you choose the bit rate, from 96 to 320 kbps. WAV and FLAC are lossless, so they have no bit rate setting.
Lossy and lossless: what conversion can and cannot do
MP3, M4A, OGG and Opus are lossy: they throw away sound the ear is unlikely to notice, which is how they get so small. WAV and FLAC are lossless: they store the sound they are given without discarding anything more. Three practical rules follow from that:
- Converting a lossy file to WAV or FLAC makes it bigger but not better. Do it only when something asks for that format.
- Each lossy-to-lossy conversion loses a little more. Always convert from the best copy you have, ideally the original recording, not from a file that has already been converted several times.
- A bit rate higher than the original's cannot add detail. Converting a 128 kbps file at 320 kbps gives a file two and a half times the size that sounds the same.
Voice notes, recordings and other awkward files
WhatsApp voice notes are usually Opus sound in a file ending .opus or .ogg, which many computers, older phones and upload forms will not open. iPhone Voice Memos are M4A, and some Android call and voice recorders save AMR or AAC files. Convert any of these to MP3 and they will play everywhere. Several transcription services and editing apps prefer WAV, so choose that when they ask for it.
You can also choose a video file here and the tool converts its sound, though video to MP3 has a setting that can copy a video's AAC sound without any loss.
What is kept and what changes
- Song tags (title, artist, album and similar) are copied into the new file.
- Cover pictures embedded in songs are not carried over.
- Surround sound is folded down to stereo for MP3, OGG and M4A; WAV and FLAC keep every channel.
- Your original file is never changed.
To cut a song or make a ringtone, use the audio cutter; to put several files together, the audio joiner; to record something new, the voice recorder.
The engine behind this tool
Video and sound are processed by FFmpeg, the open-source engine behind most of the world's video software, compiled to run inside your browser as ffmpeg.wasm. It is downloaded from this site (about 31 MB) the first time you use a video or audio tool, and your browser keeps it for next time. FFmpeg and ffmpeg.wasm are free software, licensed under the GNU General Public License version 2 or later; their source code is at github.com/ffmpegwasm/ffmpeg.wasm.