Reset to defaults
Need help?Compress audio files online with this audio compressor. Upload MP3, WAV, FLAC, M4A, AAC, OGG, Opus or WMA files, then choose how to shrink them: a quality preset, a percentage of the original size, an exact size in KB or MB, or a bitrate you type yourself. The output is MP3 unless you pick Same as source or another format under Audio File Extension.
How to compress audio files
- Upload your audio: Click Upload or drop one or more files on the page. MP3, WAV, FLAC, AAC, M4A, OGG, Opus, WMA, AIFF, AMR and AC3 are among the 21 accepted inputs.
- Choose the output format and a compression mode: Under Audio File Extension keep MP3 or pick Same as source or another format. Under File Compression keep the Very High quality preset, or switch to File Size Percentage, Specific file size, Custom Bitrate, Constant Bitrate or Variable Bitrate.
- Compress and download: Set Audio Channel, Audio Sample Rate or Trim if you need them, click Compress, then download each file or the whole batch as a ZIP.
Quality Preset
File Compression starts on Quality Preset with Very High (Recommended) selected; the ladder runs Highest, Very High, High, Medium, Low, Very Low, Lowest. The preset chooses the bitrate for the output format, so you never type a number. Use it when you have no fixed size to hit.
File Size Percentage
A slider from 1 to 100, starting at 80: a 10 MB file at 50 comes out at about 5 MB, and 100 produces no reduction. It works best when the output format matches the input; asking for a percentage while also changing format can give a poor result, and the tool warns you when that is the case.
Specific file size
Type a number and choose B, KB or MB (the field starts at 8 MB). The server reads the file's duration and picks the bitrate that lands at or just under the target; aim a little under a hard cap so container overhead does not tip you over. A target too small for the duration stops at the codec's minimum bitrate and sounds poor. Not offered for AMR or AC3 output.
Custom, Constant and Variable Bitrate
Custom Bitrate takes any value in bps, kbps or Mbps (default 64 kbps). Constant Bitrate offers fixed steps from 8 to 320 kbps for MP3 (AMR has its own 4.75 to 23.85 kbps steps). Variable Bitrate offers a range per codec, such as 45k-85k up to 220k-260k for MP3 and 6k-24k up to 320k-510k for Opus; it is not available with Same as source or WAV output. With Same as source the tool cannot check bitrate limits in advance, so an out-of-range value is replaced by the closest legal one and shown on the download card.
Channels, sample rate and trim
Audio Channel offers Original, Mono and Stereo; mono roughly halves a speech recording at the same bitrate and costs nothing audible on a single voice. Audio Sample Rate offers Original, 8000, 12000, 16000, 24000, 44100 and 48000 Hz; 16000 or 24000 Hz suits speech, music should stay at 44100 or 48000 Hz. If a bitrate does not support your choice, the tool switches to the closest value that does and reports it. Trim takes a start time and a duration in seconds or HH:MM:SS.sss.
Hitting a size limit
Mail and chat services cap attachments: 25 MB for Gmail, 25 MB for Outlook, 20 MB on Discord's free tier. Use Specific file size a little under the cap; for a long speech recording also switch Audio Channel to Mono and the sample rate to 16000 Hz so the encoder has room. If the file is an MP3 and must stay one, use the MP3 compressor.
When compression hurts
Lossy codecs discard what most listeners do not hear, and the lower the bitrate the more they discard; music shows it first on cymbals, applause and dense mixes, while speech tolerates far lower bitrates. Re-encoding an MP3 to another lossy format adds a second generation of loss, so keep Same as source where you can. A FLAC or WAV upload becomes lossy if you accept the MP3 default; choose FLAC as the output (Compression level 1 to 12, default 12) when the audio must stay bit-exact.
Frequently Asked Questions
Does the audio compressor change the file format?
By default yes: Audio File Extension is set to MP3. Choose Same as source to get the same format back, or pick any other listed format to change it on purpose.
Will compressing audio reduce quality?
With a lossy output format some detail is removed; at the Very High preset most listeners notice nothing. Lower presets, small size targets and low bitrates make the loss audible, first on music. FLAC output keeps the audio bit-exact.
Can I compress several files at once?
Yes. The same settings apply to every file in the batch; download them one by one or as a single ZIP.
Are my files private?
Files are uploaded over an encrypted connection, processed on our servers and deleted automatically after a few hours. Nothing is shared or indexed.
Related tools
- MP3 Compressor — MP3 in, MP3 out
- WAV Compressor — smaller files that stay .wav
- M4A Compressor — Apple AAC audio
- Audio Converter — change format only
- Audio Trimmer — cut to a time range