Compress Audio
Compress audio files to reduce size
Click or drop an audio file hereChoose an audio file
About Compress Audio
Compress Audio shrinks one audio file by re-encoding it at a lower bitrate. Pick 64, 96, 128, 192, 256, or 320 kbps; when ffmpeg can read your file's own bitrate, the tool never encodes above it, which keeps most small voice memos from growing, and the page says when the result is still larger. Mono and a lower sample rate make speech files smaller still. It writes nine lossy formats where a bitrate counts: MP3, AAC, M4A, OGG, Opus, WMA, AC3, M4B, and MP2. It does not touch loudness or dynamic range. Every format but Opus is encoded by ffmpeg.wasm in the page; Opus is handed to our server.
How to compress an audio file
- 1Pick or drop the audio file you want to make smaller.
- 2Choose a value under "Bitrate", from 64 to 320 kbps.
- 3For speech, check "Mono (half the data for speech)" or choose a lower "Sample rate".
- 4Pick the "Output format" and click "Compress audio".
- 5Compare the "Original" and "Compressed" sizes, then click "Download".
Formats and limits
- Input formats
- MP3, WAV, M4A, AAC, FLAC, OGG, OGA, Opus, WMA, AC3, AIFF, AIF, AMR, MKA, WEBA, CAF, MP2, M4B, M4R, WV, AU
- Output formats
- MP3, AAC, OGG (Vorbis), M4A, Opus, WMA, AC3, M4B, MP2
- Bitrate
- 64, 96, 128, 192, 256, or 320 kbps, lowered to the source's own bitrate when ffmpeg can read it and it is lower (never under 8 kbps)
- Sample rate
- Keep the original, or 48, 44.1, 32, 22.05, 16, or 8 kHz; OGG, AC3, and MP2 take only 48, 44.1, or 32 kHz. Mono and sample rate are not offered for Opus.
- Maximum file size
- 750 MB on a computer, 300 MB on a phone or tablet; a larger file is refused as soon as you choose it.
- Usage limits
- Opus only: jobs per connection are limited per hour and per day, and the decoded audio sent to our server has a maximum size and length.
Where your file is processed
Compression runs in your browser with ffmpeg.wasm, fetched from unpkg.com, except when you choose Opus. Then the audio is decoded here to FLAC and sent to our server, which encodes it with libopus at your bitrate; the decoded copy is deleted there when encoding ends, and the compressed file after your browser has downloaded it or after 15 minutes. If compression fails, the cleaned error message, the tool name, the file extension, a size range, and your browser's name and version are reported to us.
Frequently asked questions
Does this compress the dynamic range (loud versus quiet)?
No. Despite the name, it only lowers the bitrate to make the file smaller. Loud and quiet passages keep their levels. To even out loudness instead, use the normalization option of Boost Audio.
Can the result be larger than my file?
Yes, when your file is already well compressed. The page then shows "Larger by" and advises keeping your original. To avoid most such cases, the tool never encodes above the bitrate your file already has, when ffmpeg can read it, and says so when it lowered your choice.
Can I compress to WAV or FLAC?
No, on purpose: a bitrate target does not shrink these lossless formats. The list holds nine lossy formats where a lower bitrate gives a smaller file. For lossless audio, Audio Converter can write FLAC, WavPack, or ALAC instead.
Which output goes through a server?
Opus alone: the decoded audio is sent to our server for libopus encoding at the bitrate you chose. That service limits jobs per connection per hour and per day and refuses audio over its maximum size or length. The eight other formats are encoded by ffmpeg.wasm on this page.
Tips and tricks
- ✓Cut silences or unwanted parts with Trim Audio first: a shorter file is a smaller file.
- ✓Check your file's current bitrate with Audio Metadata Viewer before choosing a lower one.