orbitHow to compress an audio file
- Click Choose an audio file and select a recording from your device. MP3, WAV, M4A, AAC, OGG, Opus and FLAC files work in most browsers.
- Pick a preset. “Balanced” (128 kbps) is a good starting point for music, “Voice or podcast” (64 kbps mono) for speech. You can also set the quality, channels and sample rate yourself.
- Check the estimated size shown under the settings, then press Compress audio. A progress bar shows how far along the encoding is.
- Press play to listen to the result, compare the sizes, and press Download if you are happy with it.
How much smaller will my file get?
The size of an MP3 file is simply its bitrate multiplied by its length: 128 kbps is about 1 MB per minute, 64 kbps about 0.5 MB per minute and 320 kbps about 2.4 MB per minute. A WAV file or a 320 kbps recording therefore shrinks dramatically at 128 kbps, while a file that is already a 128 kbps MP3 will not get smaller at all. If the result is not smaller than the original, the tool tells you instead of handing you a worse file.
Choosing the right settings
- 192 kbps and above — close to the original for most listeners. Use it for music you want to keep.
- 128 kbps — the everyday choice for music on phones and in the car. Files are roughly one tenth the size of CD-quality WAV.
- 64 kbps mono — clear speech for podcasts, lectures, voice messages and meeting recordings.
- 32 kbps mono, 22 kHz — the smallest option. Fine for spoken notes, not for music.
Lowering the sample rate removes the highest frequencies. 22.05 kHz and 16 kHz are suitable for speech only. At sample rates below 32 kHz, MP3 allows at most 160 kbps, and the tool adjusts the quality automatically.
Good to know before you compress
Compressing is a one-way step: a lossy format such as MP3 discards detail that cannot be restored, and compressing a file that is already lossy removes a little more. Keep your original if it matters. The result is always an MP3 file, which plays on practically every phone, computer, car stereo and web page. Text tags and cover art of the original file are not copied into the new file.
Everything happens on your device: your browser decodes the recording and the open-source LAME encoder, compiled to JavaScript, writes the MP3. The audio is never uploaded, so private recordings such as interviews, meetings and voice memos stay private.
Frequently asked questions
Which formats can I open?
Whatever your browser can play. MP3, WAV and M4A/AAC work everywhere. OGG, Opus and FLAC work in Chrome, Edge and Firefox, and in current versions of Safari. If a file cannot be opened, convert it to MP3 or WAV first.
How can I get a recording under an upload limit such as 10 MB?
Divide the limit by the length. A 10 MB limit for a 20-minute recording allows about 0.5 MB per minute, which is 64 kbps. Choose the “Voice or podcast” preset and check the estimated size before you start.
Is there a size limit?
Files up to 60 MB and about one hour of audio can be processed. Long recordings need a lot of memory while they are decoded, so very long files work best on a computer.
Why is the output at 44.1 kHz by default?
Audio is converted to 44.1 kHz, the CD standard, while it is decoded. Choose 48 kHz if you need it, or a lower rate for a smaller speech file.