Quick presets
Audio is compressed on your device. Nothing is uploaded.
How to compress an MP3
Drop one or more MP3 files into the tool, or pick a preset. The new size estimate updates the moment you change a setting, and encoding starts on its own a second later. When it's done, play both versions and use the switch button to flip between them at the same moment in the track. That's the quickest way to hear whether a lower bitrate costs anything.
You can drop in WAV, M4A, OGG and FLAC files too. They're converted to MP3, which is often the biggest saving of all.
Which bitrate should you use?
| Bitrate | Good for | Size per minute |
|---|---|---|
| 32 to 48 kbps mono | Voice memos, lectures, audiobooks | About 0.25 to 0.35 MB |
| 64 kbps mono | Podcasts and interviews | About 0.5 MB |
| 96 to 128 kbps stereo | Music for phones, sharing and background listening | About 0.7 to 1 MB |
| 160 to 192 kbps stereo | Music where you want near-original quality | About 1.2 to 1.4 MB |
| 256 kbps stereo | Archiving and critical listening | About 1.9 MB |
Compressing can't add quality back. If your MP3 is already 128 kbps, saving it at 192 kbps only makes the file bigger. The tool tells you when that happens.
Mono and sample rate
Most speech is recorded in mono or might as well be, so switching to mono lets the encoder spend the whole bitrate on one channel. That's why 64 kbps mono sounds clearer for a podcast than 64 kbps stereo. For voice, dropping the sample rate to 22 kHz or 16 kHz trims high frequencies speech doesn't use and lets lower bitrates sound cleaner. Keep the original sample rate for music.
Trimming silence and normalizing
Trim silence removes dead air at the start and end of a recording, which is common on voice memos and meeting recordings. Normalizing raises the overall volume so the loudest peak sits just below the maximum, which helps quiet recordings without distorting them. Neither changes anything in the middle of the audio.
Frequently asked questions
Will my song titles and album art be kept?
Yes, with Keep tags and cover art turned on. The tool copies the original ID3 tags, including embedded artwork, into the compressed file. Turn it off if you want the smallest possible file, since cover art can add a few hundred kilobytes.
Does compressing an MP3 reduce quality?
Re-encoding at a lower bitrate always loses some detail, but at 128 kbps and up most people can't hear the difference on phones and laptop speakers. Use the switch button to compare for yourself before downloading.
How long does it take?
A typical four-minute song encodes in a few seconds on a modern computer. Long recordings like hour-long podcasts can take a minute or two. Phones are slower. The progress bar shows how far along it is.
Can I compress several MP3s at once?
Yes. Add as many as you like. They're encoded one after another with the same settings, and Download all gives you a single ZIP.
Are my files uploaded?
No. Decoding and encoding both happen in your browser, so your audio never leaves your device.