Compress MP3 Online
Processing entirely on your device — large files may take a moment.
The quality slider maps straight to the MP3 bitrate — 40 lands near 64 kbps for voice, 90 near 190 kbps for music. Every file is re-encoded once with LAME, the reference MP3 encoder.
One rule of thumb: re-encoding a lossy file always loses a little more fidelity. For maximum shrink on music, aim for the lowest bitrate that still sounds right to you.
How to compress MP3
- 1
Select your files
Drag & drop your MP3 files onto the area above, or click to browse. You can add multiple files at once for batch conversion.
- 2
Convert instantly
Click "Compress" and pick a quality level — lower quality means a smaller file. Everything runs inside your browser; nothing is uploaded.
- 3
Download results
Download each converted MP3 file individually, or grab everything at once as a ZIP archive.
About the MP3 format
MP3 (MPEG-1 Audio Layer III) defined digital music: standardized in 1993, popularized by Napster and the first portable players, and freed of all patents in 2017. It is lossy psychoacoustic compression — it discards frequencies the ear supposedly won't miss — at bitrates from 128 to 320 kbps, with ID3 tags carrying title, artist and cover art.
Twenty years of competitors have failed to displace it, because playback support is absolute: every device that has ever played music plays MP3. At 320 kbps even critical listeners struggle to identify it in blind tests, though modern codecs reach the same quality at noticeably lower bitrates.
+Strengths
- ✓Plays on absolutely everything
- ✓Rich tag ecosystem (ID3, cover art)
- ✓320 kbps is transparent for most listeners
!Limitations
- −Lossy ceiling — never a mastering format
- −Less efficient than AAC/Opus at equal quality
- −Low-bitrate artifacts are audible and permanent
Frequently asked questions
How much smaller will my MP3 get?
Roughly proportional to the bitrate drop: 320→96 kbps is about 70% smaller. Voice content survives aggressive drops far better than music.
Can I compress WAV or M4A here?
This page is MP3-only. Convert other formats to MP3 first — the converter pages accept WAV, M4A, FLAC and 50+ more inputs.
Is the metadata (ID3 tags) kept?
Artwork and tags written by your music library generally do not survive the re-encode; the audio itself is what matters here.