Audio Compressor

WhatsApp caps documents at 2 GB but most email servers stop at 25 MB, course portals at 10–50 MB, and some job application forms at 5 MB. A voice memo or podcast episode exported at studio settings easily blows past those limits.

This tool reduces audio file size by re-encoding to MP3 with sensible presets: good-quality music, smaller music, podcast voice, voice notes, and a smallest-possible speech setting at 32 kbps. Each result shows how much smaller it got.

Note that “compressor” here means file-size compression, not dynamic-range compression (the studio effect that evens out loud and quiet parts). There is, however, an optional normalize switch that raises quiet recordings to full level.

The presets are opinionated on purpose. Most people don't know whether they want 96 kbps or 128 kbps; they know they have a voice memo or a song and a size limit. Pick the preset that describes the content and the tool chooses the channel count, sample rate and bitrate that suit it.

How It Works

1. Add recordings — MP3, WAV, M4A, OGG, OPUS, FLAC or WebM, up to 20 files.
2. Pick a target — each preset sets bitrate, channels and sample rate together (for example, voice note = 64 kbps mono at 44.1 kHz; smallest = 32 kbps mono at 22.05 kHz). Optionally normalize the peak level to −0.2 dBFS.
3. Re-encode — audio is decoded, resampled with an OfflineAudioContext, and encoded to MP3 with lamejs. Each result lists the percentage saved.

Compatibility & Support

Supported Input → Output Formats

• Input: MP3, WAV, M4A/AAC, OGG, OPUS, FLAC, WebM audio
• Output: MP3 at 32–128 kbps, mono or stereo
• Typical saving: 80–95% from WAV, 30–70% from high-bitrate MP3 or M4A

Unsupported Formats

Formats other than MP3 are not produced here — MP3 is the one every phone, car stereo, browser and email client plays. If you specifically need a smaller lossless file, FLAC is the answer, and that requires desktop software. Re-encoding a file that is already small (for example a 64 kbps MP3 voice note) may not reduce it further — the result list says so, and you should keep the original. Decoding uses your browser's built-in codecs. Chrome and Edge read MP3, WAV, AAC/M4A, OGG Vorbis, Opus, FLAC and WebM audio; Firefox is similar but has no AAC on some Linux systems; Safari reads MP3, AAC/M4A, WAV, FLAC and, from recent versions, Opus.

File Size Limits

Up to 20 files per batch and 300 MB per file. Audio is decoded to uncompressed samples in memory, so a one-hour stereo recording needs roughly 1.3 GB of RAM while it is processed. On phones, split long recordings or convert them one at a time.

Who Should Use This Tool?

• Students: A student shrinks a 60 MB WAV presentation recording to under 10 MB for an LMS upload.
• Freelancers & Designers: A podcaster creates a 96 kbps mono version of an episode for listeners on slow mobile data.
• Office Professionals: A manager compresses a 45-minute meeting recording to 32 kbps so it fits in an email to absent colleagues.
• Developers: A developer reduces bundled audio assets for a progressive web app to keep the install size small.

Why This Tool Beats the Alternatives

• Presets tuned for real uses instead of a bare bitrate list.
• Honest when a file can't get smaller.
• Private processing for meetings and interviews.
• No account or watermark, no per-minute limits.
• Normalize option built in.

Pro Tips

• Speech stays perfectly understandable at 64 kbps mono; music starts to sound thin below 96 kbps.
• Trim silence and unwanted sections first with the Audio Trimmer — shorter is smaller.
• Don't repeatedly compress the same file; always start from the best-quality original. Every lossy generation stacks artifacts, and a second pass at the same bitrate saves almost nothing.

Add your recordings above, pick a target, and download smaller MP3s.