Audio Compressor
Reduce audio file size by adjusting bitrate
Your files are processed on your device. The first use downloads a processing engine, which your browser then keeps.
Drop an audio file to compressTap to choose an audio file to compress
or click to browseor tap to choose
Reduce audio file size
Large files (over 500 MB) may take longer or run out of browser memory
About Audio Compressor
Reduces an audio file's size by lowering its bitrate (down to 32 kbps), optionally converting to mono or aiming at an exact size in MB, useful for fitting an email attachment limit or saving storage space. Medium/Strong target a real reduction (roughly 25-30% / 50% smaller; the exact saving is shown after the run), calculated directly from the file's length — audio bitrate encoding is predictable enough that this doesn't need trial-and-error the way video compression does. Runs entirely in your browser — the audio never leaves your device.
Upload your audio file, pick Medium or Strong for a targeted reduction, or choose a specific bitrate manually if you want direct control.
128 kbps is a reasonable, widely-used balance for spoken word and most music. Go lower (64-96 kbps) for voice memos or podcasts where small size matters more than audio fidelity, or higher (192-256 kbps) for music where quality matters more.
Watch: Audio Compressor in Action
- What bitrate should I use for a voice memo versus music?
- 128 kbps is a reasonable, widely-used balance for spoken word and most music. Go lower (64-96 kbps) for voice memos or podcasts where small size matters more than fidelity, or higher (192-256 kbps) for music where quality matters more.
- How does this calculate the target file size?
- It's calculated directly from the file's length — audio bitrate encoding is predictable enough that hitting a target size doesn't need the trial-and-error search that video compression requires.
- Will the output always be an MP3?
- Yes. Whatever you upload, the compressed file is encoded as MP3 with the bitrate chosen by the mode, and the download name ends in .mp3. If you need to stay in the original format, this tool is not the right choice.
- How does Target size work?
- You type a size in MB. The tool divides 97 percent of that by the file's length to find a bitrate, never going below 32 kbps, and encodes once. Because MP3 overhead varies, the result can land slightly off, and extremely small targets come out larger than asked.
- Why are some bitrates greyed out in Manual Bitrate?
- Any value at or above the file's own bitrate cannot make it smaller and often makes it bigger, so those chips are disabled. The note beneath shows the roughly measured bitrate of your file, which tells you which values are usable.
- Why did it say the file is already well compressed?
- The re-encoded MP3 came out the same size or larger than your original, which happens with already efficient files such as Opus voice notes. Rather than hand you a worse file, the tool shows no download and suggests keeping the original.
- Does Convert to mono really halve the file size?
- Not by itself. The bitrate you or the preset chose is applied either way, so the size stays near that target. Mono gives a single voice the whole bitrate, which can sound a little cleaner at low settings, but it is not a size guarantee.
How to use Audio Compressor
Drop an audio file, then choose how to shrink it. Medium (25% smaller) and Strong (50% smaller) aim at that reduction, calculated from the file's size and length. Manual Bitrate shows chips for 32, 48, 64, 96, 128, 160, 192 and 256 kbps and a slider; values at or above the file's own bitrate are greyed out. Target size takes a number of MB, with quick buttons for 2, 5, 10 and 25 MB.
Tick Convert to mono if the recording is a single voice. Press Compress Audio, then compare the Original and Compressed players side by side and download compressed_ followed by your file name, ending in .mp3.
When to use it
Reach for it when a voice recording is too large to email or upload to a form, when a WAV or FLAC export needs to become something portable, or when you have a target such as getting a lecture under a fixed number of megabytes. Target size is the quickest route when a limit is stated in MB.
When not to use it
Do not use it as an archive format for music you want to keep intact, because the output is always lossy MP3. If the file is already small, such as an Opus voice note, converting to MP3 would make it larger, and the tool will tell you to keep the original. For simple format changes without a size goal, use the Audio Converter.
Tips for best results
WAV and FLAC shrink dramatically whatever preset you pick, so Light is often enough for them. For speech, 64 to 96 kbps is usually fine; music deserves 128 kbps or more. In Target size mode the tool aims 3 percent under your number to leave room for tags. A stated size below the 32 kbps floor will come out slightly larger than asked.
Limitations
The output is always MP3 regardless of the input, and the lowest bitrate it will use is 32 kbps. The Medium and Strong figures are targets; if reaching one would need a lower bitrate than that floor, the file shrinks as far as it can and says so. No compressed file is offered if the result is not smaller than the original.
Privacy
Re-encoding to MP3 runs on an engine inside your own browser, so the audio is not uploaded, and the compressed result is held only in the page until you download it. The Original and Compressed players use local blob addresses. The single fetch tied to the tool is the engine itself, roughly 25 MB from a public CDN, requested when you press Compress Audio.
More from Audio Tools: