Compress MP3
Shrink MP3s to send, upload or fit on a phone, on your own device.
- Nothing is uploaded
- Works offline after first use
- Open source
- No watermark · limit is your device’s memory; phones hold less
Make MP3 files smaller in your browser: pick a lower bitrate or a size limit for email and Discord. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The size limit is your device’s memory, and phones hold less; give the page a short while after your first run to save itself for offline use, and then it works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
An MP3’s size is its bitrate times its length. A 320 kbps song takes about 2.4 MB a minute; at 96 kbps it is 0.7 MB, still clear for podcasts, audiobooks and voice. This page re-encodes each MP3 at the bitrate you choose, or at whatever bitrate fits a size limit, entirely in your browser.
Nothing is uploaded, so recordings of meetings and lectures stay on your machine, and there is no daily file limit. If an MP3 is already smaller than the setting would make it, you get the original back instead of a worse copy.
For an audiobook or a podcast on a phone, Small at 96 kbps keeps the voice clear at three quarters of the size of a 128 kbps file, and ticking Mono gives all of that bitrate to one channel. For a song you still want to enjoy, Light at 160 kbps sounds the same as the original to most people. When the file has to go somewhere with a limit, leave the compression where it is and choose a Fit under size: the page works out the bitrate from the length and steps down only as far as it has to.
As a rough guide, 25 MB holds about 25 minutes of stereo MP3 at 128 kbps and about 50 minutes at 64 kbps. The 8 MB setting fits about 16 minutes at 64 kbps. The lowest step is 32 kbps, so if a very long file still comes out over the limit, the result says so; cut it into parts with the MP3 cutter and compress each one.
How it works
- Drop one or more MP3 files, or tap to pick them.
- 96 kbps is already chosen. Pick a size limit for email or Discord, and Mono for speech.
- Compress. Each MP3 downloads when it is ready; several come as a zip.
In your browser, not on a server
Your browser decodes the sound with its own audio decoders. When you set a size limit, the bitrate is worked out from the length of the sound so the file lands under it. The smaller file is then written in your tab, as MP3 by LAME compiled to WebAssembly or as OGG by the browser’s own Opus encoder (WebCodecs) with Mediabunny (MPL-2.0) writing the container.
Compared with upload-based tools: Online audio compressors upload the recording before they shrink it, which for a large WAV is the slowest part, and cap free files at 50 to 100 MB. Here nothing is uploaded, so the limit is your device’s memory (phones hold less) and private recordings stay on your device.
Verify it yourself. Give the page a short while after your first run to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Does compressing an MP3 lose quality?
Yes, a little: it is decoded and encoded again at a lower bitrate. For speech at 64 to 96 kbps nobody notices; for music, stay at 128 kbps or above.
What bitrate is my MP3 now, and will compressing it help?
Divide the file size by its length: about 2.4 MB a minute is 320 kbps, 1.4 MB is 192 kbps and 1 MB is 128 kbps. Compressing only helps when the setting is lower than that. If it is not, you get your original file back, marked as already smaller, rather than a copy that is worse and no smaller.
Can I send an MP3 on Discord without Nitro?
At the time of writing, free Discord accounts can upload files up to 10 MB. Choose 8 MB (Discord) under Fit under, which leaves some room, and the MP3 comes out small enough. A song of about four minutes fits at 160 kbps and a half hour talk at 32 kbps; anything much longer has to be split into parts first.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. Give the page a short while after your first run to save itself for offline use; then you can turn off Wi-Fi and it still works.
More video and audio tools
Compress audio
Shrink recordings, podcasts and songs to send or store. Done on this device, never uploaded.
Video background remover
The person stays, the room goes: blurred, a flat colour or a picture of your choice, done frame by frame on your own device.
Audio splitter
Cut one long recording into separate files at the times you choose or at equal lengths. Done on this device, and the file is not uploaded.
Video to MP3
Pull the sound out of a video, or turn any audio file into an MP3. Your files are converted on this device and never uploaded.
Other conversions
Guides
- How to reduce MP3 sizeAn MP3 gets smaller when you lower its bitrate, make it mono, shorten it, or switch format. Here is what each saves, with measured results.