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MP3 Compressor

Reduce an MP3 file’s bitrate to make a smaller listening copy. Compare the input and output sizes, then listen for changes before keeping the result.

Audio and transcripts stay on your device. Processing runs in your browser.
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Choose a file

MP3. Up to 100 MiB per file (50 MiB on touch devices), 1800 seconds. Decoded audio memory limits also apply.

    Settings

    Bitrate applies to MP3 and AAC. WAV uses 16-bit PCM; FLAC is lossless. OGG uses quality-based encoding.

    Result

    Your result will appear here

    Add a file, pick your settings, then select Compress MP3.

    No account or daily usage quota. File and device limits protect your browser from running out of memory.

    Processing audio

    Checking your settings…

    How to use MP3 Compressor

    1. Choose an MP3 file from your device.
    2. Choose a bitrate. Lower settings usually reduce size and remove more audio detail.
    3. Keep stereo or choose mono for a recording that does not need separate channels.
    4. Press Compress MP3, compare the sizes and listen before downloading.

    Bitrate sets the main size budget

    For approximately constant bitrate audio, encoded audio size is bitrate × duration ÷ 8. A 3-minute recording at 128 kbps has about 2.88 MB of encoded audio before metadata and container overhead. At 64 kbps the audio budget is about half that.

    An MP3 may already use a low bitrate. Re-encoding it at a higher setting can make it larger without restoring detail. The tool shows a warning when the result is at least as large as the input.

    Listen for damage before choosing the smallest file

    Speech often tolerates lower bitrates than dense music. Compare consonants, room noise and pauses in a voice recording. For music, check high percussion and sustained sounds. There is no setting that guarantees transparent sound for every source.

    If unwanted audio is taking up space, MP3 Cutter can remove a section before you compress the remainder.

    Before you download

    • Re-encoding MP3 is lossy and cannot be undone.
    • A lower selected bitrate does not guarantee a smaller result for every input.
    • This is bitrate reduction, not loudness normalization or dynamic-range compression.

    Frequently asked questions

    Why did my MP3 get larger?

    The input may already have a lower bitrate than the setting you chose, or contain less overhead. Choose a lower bitrate and compare again.

    Can I compress without losing quality?

    Re-encoding MP3 discards some information. Keep the source if you need its existing quality. Trimming unwanted audio can reduce duration without relying only on bitrate.

    What is the difference between mono and stereo?

    Mono stores one channel. Stereo stores left and right channels. Downmixing can suit speech but changes spatial information in a stereo recording.

    Does this make quiet audio louder?

    No. It reduces the encoding bitrate. It does not normalize loudness or compress the recording’s dynamic range.

    Often used together with MP3 Compressor.

    • MP3 Cutter

      Trim MP3 audio with waveform positioning and exact time fields.

    • Audio Converter

      Convert between common audio formats with bitrate and channel controls.

    • WAV to MP3

      Make a smaller, shareable MP3 copy of a WAV recording.