Browser Optimiser

Audio Compressor

Choose MP3 bitrate, sample rate and channels, preview the result, and download a smaller copy when those settings reduce its size.

MP3BitrateMonoEstimate

Upload an audio file to draw the waveform

00:00.000 Compressed preview 00:00.000

Sample rate Channels

Upload audio to estimate output size.

Compress MP3 for a smaller sharing copy

This tool reduces file size by re-encoding audio. It is different from a dynamics compressor, which changes the difference between quiet and loud passages. MP3 encoding is lossy: keep your original and listen to the downloaded copy.

Choose settings, then check the download

Choose a browser-supported file and wait for decoding.
Select MP3 and a bitrate. For WAV output, choose sample rate and channels; MP3 bitrate does not apply.
Use Preview to check the processed audio, export, then compare the actual download size and sound with your source.

A lower sample rate changes the available audio bandwidth, and mono combines the channels. These are listening tradeoffs, not lossless MP3 compression. At a fixed MP3 bitrate, those changes do not guarantee a smaller file. Increasing settings or exporting an MP3 as WAV can make the file larger.

Understand the size estimate

The MP3 estimate uses duration × bitrate ÷ 8. It excludes encoding overhead and padding, so the actual download can differ. WAV estimates use the selected sample rate, channels and 16-bit samples plus the WAV header. An estimate is not an exact target-size guarantee.

Worked example, checked 15 October 2026: a 10-second stereo test file exported at 128 kbps and 44.1 kHz had an MP3 estimate of 160,000 bytes and an actual size of 160,496 bytes. Choosing mono at the same settings produced the same size. A 22.05 kHz mono WAV export was 441,044 bytes, matching its estimate. These are examples, not promises for your file.

Read how to reduce MP3 file size for sharing and how to choose MP3 bitrate. Use the Audio Converter when you only need a format change.

About This Tool

Reduce output size with MP3 bitrate, sample-rate, and mono controls.

For MP3, bitrate is the main file-size control; mono or a lower sample rate does not guarantee a smaller file at the same bitrate. PCM WAV size depends on duration, sample rate and channel count. This tool changes file size, not audio dynamics.

Practical tips

Use mono for speech when stereo is unnecessary.
Preview low sample rates before exporting.
Treat the estimate as a guide; compare the actual download size and listen for tradeoffs.

Common questions

Which setting reduces size the most?

For MP3, choose a lower bitrate and compare the actual download. At a fixed bitrate, mono does not automatically halve MP3 size. Lower sample rate or fewer channels reduce PCM WAV audio data.

Does a smaller file always sound worse?

Lower bitrate, sample rate or channel count can remove information. What is acceptable depends on the source and use: preview, export and listen to the downloaded copy.

Is compression performed on a server?

No. Resampling, channel conversion, and encoding run locally in the current browser tool.