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Audio compressor

Free online tool to reduce audio file size by lowering MP3 bitrate and exporting compressed audio locally in your browser

Upload audio

Output audio

Choose a file and start processing. The output audio will appear here.

About this tool

Audio compression here reduces file size through a lower lossy encoding bitrate for uploads, messaging, and web delivery. It differs from dynamic-range compression, which changes the gap between loud and quiet passages; this tool primarily changes encoded data volume.

Acceptable settings depend on content. Solo speech usually tolerates lower bitrate than complex music, while background noise, reverberation, and high-frequency instruments consume more coding capacity. Judge by listening instead of pursuing the smallest number alone.

How to use it

  1. Upload and note source size

    Check source quality and duration and avoid another generation from heavily compressed input when possible.

  2. Choose a target bitrate

    Begin with the highest value that can meet the size need and step down for comparison.

  3. Listen and compare

    Check sibilance, metallic artifacts, stereo image, and quiet passages before downloading.

Supported range and limits

How it compresses
Re-encodes MP3 at a lower bitrate; duration, sample rate and channel count are unchanged
Typical result
320 kbps down to 128 kbps saves roughly 60%; whether speech suits a lower step depends on the source and an actual listening check
Irreversible
A lossy re-encode. High frequencies already discarded do not return if you raise the bitrate later
Poor candidates
Files that are already low-bitrate; compressing again degrades audibly for little saving
vs Change Bitrate
This one frames the choice around shrinking the file; Change Bitrate is for hitting an exact number
Where it runs
FFmpeg compiled to WebAssembly in your browser; the file is never uploaded

When you would use it

  • Meeting an attachment limit

    Reduce a recording to fit an email, form, or messaging platform.

  • Optimizing spoken delivery

    Create a smaller podcast preview, course narration, or voice-note version.

  • Getting speech under an attachment limit

    A lower bitrate can reduce a meeting recording substantially, but the result still needs an actual listen before delivery.

What to know before you start

  • Lower bitrate permanently discards sound information, so keep a high-quality original.
  • Size also depends on duration and channels; twice the duration needs roughly twice the data at one bitrate.
  • Dynamic-range compression, loudness normalization, and codec compression are separate processes.

Related concepts

codec compression
An encoding process using perception to reduce the amount of data representing sound.
dynamic range
The level difference between the quietest and loudest audio passages.

Frequently asked questions

How does audio compression reduce size?
It lowers the MP3 bitrate to shrink the file; the lower the bitrate the smaller the file, with a matching drop in quality.
Does compressing upload my file?
No. Compression runs locally in your browser and the audio is never uploaded.
How do I balance size and quality?
Use a lower bitrate for speech and keep a higher bitrate for music; listen back before settling on a level.
Will anyone notice the compression?
It depends on the source, content, and listening equipment. Speech often tolerates a lower bitrate better than music, but no single setting is transparent for every file. Listen for vocal sibilance, background noise, and high-frequency instruments before keeping the result.
How does this differ from Change Bitrate?
Underneath it is the same operation; re-encoding at a lower bitrate. Only the framing differs: this one is organised around making the file smaller, while Change Bitrate is for hitting an exact number a format demands.
Can I compress an already-compressed file again?
Technically yes, but each pass discards information on top of what is already gone and the degradation stacks visibly. When you need it smaller, go back to the original and compress once, rather than compressing twice.

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