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Audio Compressor: Compress MP3 and Audio Files

Make a recording small enough to email or upload. Choose a bitrate or a target size, see the size before and after, and download a smaller MP3. Free, no account, and the file is not uploaded.

This compressor makes the file smaller. It is not a dynamic range compressor, the effect in music production that evens out loud and quiet parts.

Drop your audio file here or click to browse

MP3, WAV, M4A, AAC, MP4, OGG, WEBM, FLAC or OPUS, up to 100 MB and 30 minutes.

The file is converted in your browser and is not uploaded.

How to compress an audio file

Three steps, all in your browser.

  1. 1

    Drop the file

    Drag an MP3, WAV, M4A or other audio file onto the compressor. It shows the original size straight away and, for most formats, the length and an estimate of the new size.

  2. 2

    Choose a bitrate or a size

    Pick a bitrate yourself, or choose Fit under 25 MB for an email attachment, or enter any size limit. The compressor picks the highest bitrate that fits. Turn on mono for a voice recording.

  3. 3

    Download and compare

    The result shows the original size, the new size and the percentage saved. Play it in the preview before you send it, and keep the original if you may need the full quality later.

Starting from a WAV recording? The WAV to MP3 Converter explains how much smaller each bitrate makes it.

MP3 size by bitrate

Computed from the bitrate (bits a second × seconds ÷ 8), the same for mono and stereo.

Bitrate1 minute10 minutes30 minutes
32 kbps234 KB2.3 MB6.9 MB
48 kbps352 KB3.4 MB10.3 MB
64 kbps469 KB4.6 MB13.7 MB
96 kbps703 KB6.9 MB20.6 MB
128 kbps938 KB9.2 MB27.5 MB
192 kbps1.4 MB13.7 MB41.2 MB
320 kbps2.3 MB22.9 MB68.7 MB
One MB here is 1,048,576 bytes, the unit the compressor shows. A 30-minute recording fits under 25 MB at 96 kbps or less.

Why speech compresses so well

A voice uses a narrow part of the frequency range, and a recording of one or two people talking has far less going on than music. An MP3 encoder spends its bits on what you can hear, so speech stays clear at bitrates that would make music sound thin.

Mono helps too. An MP3's size depends only on its bitrate, not on its number of channels: a 64 kbps file is the same size in mono or stereo. In mono all 64 kbps go to one channel, the same per-channel bitrate as 128 kbps stereo at half the size. A voice recording rarely needs two channels, so mono plus a low bitrate is the smallest file that still sounds right.

Size limits you may be aiming for

  • Email attachments

    Gmail's limit for personal accounts is 25 MB; a bigger attachment is sent as a Google Drive link instead. Other email services set their own limits, often lower, so check yours and use Fit under a size I choose.

  • Upload forms and apps

    Job applications, course portals and support forms often set their own upload limit. Enter that limit as your target size and the compressor picks the bitrate.

  • Messaging and storage

    Smaller files send faster on a slow connection and take less room in a shared drive. For a meeting or lecture archive, 64 kbps mono keeps the voices clear at about 0.46 MB a minute.

What this compressor does not do

  • Files over 30 minutes or 100 MB

    The browser holds the whole recording in memory while it works, so files are limited to 30 minutes and 100 MB. Split a longer recording into parts first.

  • Lossless output

    MP3 is a lossy format: each re-encode drops a little detail. Compress from the best copy you have and keep that original.

  • Loudness or dynamics

    It does not change volume or even out loud and quiet parts. For that you want a dynamic range compressor in an audio editor.

If the goal is for someone to know what was said, send text instead: the Audio to Text Converter takes files up to 100 MB and 10 minutes.

Send what was said, not a file

Shrinking a file so you can send it is a workaround. ParrotNotes records on your phone and shares the transcript and summary instead of a file.

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Related tools

Audio compressor FAQ