UtilityKit

500+ fast, free tools. Most run in your browser only; Image & PDF tools upload files to the backend when you run them.

Audio Compressor

Shrink MP3, WAV, M4A, OGG and FLAC files by re-encoding at a lower bitrate. Choose 32–320 kbps, pick MP3, OGG or M4A output, then download. 100% browser-side via ffmpeg.wasm.

About Audio Compressor

Audio Compressor reduces the file size of any common audio file by re-encoding it at a lower bitrate. Drop in an MP3, WAV, M4A, OGG or FLAC, choose a target bitrate between 32 and 320 kbps, pick an output format (MP3, OGG Vorbis, or M4A AAC), and download the smaller result. The whole pipeline runs locally in your browser via ffmpeg.wasm — your audio never leaves your device, there is no upload, no signup, and no watermark. Compression is lossy by design: each step down in bitrate trades audible fidelity for size. The tool exposes the bitrate slider directly so you can pick the sweet spot for your use case (voice memos compress to 64 kbps cleanly; music for casual listening usually does well at 128–192 kbps).

Why use Audio Compressor

Reduces audio file size

Reduces audio file size by 50–90% with controllable quality

Works on MP3

Works on MP3, WAV, M4A, OGG and FLAC — no preconversion required

100% private

100% private — files are processed locally via ffmpeg.wasm

No watermark

No watermark, no signup, no daily limits

Outputs to MP3

Outputs to MP3, OGG or M4A so the result plays anywhere

Cached engine means subsequent

Cached engine means subsequent compressions start instantly

How to use Audio Compressor

  1. Click or drag your MP3, WAV, M4A, OGG or FLAC file onto the upload area.
  2. Choose an output format — MP3 is the safest universal pick.
  3. Slide the bitrate slider to your target — lower values are smaller files but rougher quality.
  4. Click 'Compress & Download' to start re-encoding.
  5. Wait for ffmpeg.wasm to finish (a few seconds for short files, longer for full albums).
  6. Preview the result in the inline player and click Download to save the smaller file.

When to use Audio Compressor

  • Emailing a podcast preview that exceeds an attachment limit
  • Trimming a sound-effects library down for mobile games
  • Sharing voice memos over slow connections
  • Cutting Dropbox / Drive storage usage for archived recordings
  • Hosting larger audio catalogues on a free static-site plan
  • Preparing background music for low-bandwidth web pages

Examples

Podcast episode for email

Input: 60-minute WAV recording at 44.1 kHz / 16-bit (~600 MB)

Output: 60-minute MP3 at 96 kbps mono (~42 MB) — fits in most attachment limits

Game SFX pack

Input: 200 short WAV files totalling 80 MB

Output: Same 200 files as 96 kbps OGG (~12 MB) — small enough to bundle in a web build

Music sample for sharing

Input: 5-minute FLAC at 1411 kbps (~50 MB)

Output: 5-minute MP3 at 192 kbps (~7 MB) — good for casual listening

Tips

  • For voice-only audio, 64 kbps mono is usually indistinguishable from 128 kbps stereo and half the size.
  • Music below 96 kbps starts losing high-frequency detail — listen on headphones before committing to that bitrate.
  • OGG Vorbis is denser than MP3 at the same bitrate but less universally supported on Apple devices.
  • M4A (AAC) usually beats MP3 in quality below 128 kbps and is supported across modern phones and browsers.
  • Re-compressing an already lossy file (e.g. 192k MP3 → 128k MP3) compounds the artifacts — start from the highest-quality source you have.

Frequently Asked Questions

Does my audio leave my device?▾
No. ffmpeg.wasm runs entirely in your browser; the file is never uploaded to any server.
Will compression damage the audio?▾
Yes — re-encoding at a lower bitrate is lossy by definition. Use a higher bitrate or a denser codec (OGG / AAC) if quality matters.
What's the smallest bitrate I can use?▾
32 kbps. That's only acceptable for low-quality voice; music is unlistenable below ~64 kbps.
Can I keep the original format?▾
Output is limited to MP3, OGG and M4A — pick the one closest to your input. Lossless formats (FLAC, WAV) are not offered as outputs because the goal is size reduction.
Why does the first run take so long?▾
ffmpeg.wasm is ~30 MB and downloads once. After that it's cached in browser storage and starts instantly, even offline.
Is there a maximum file size?▾
No server cap. Browser memory limits the practical size; multi-hour recordings work but may take a minute or two to encode.
Does it work on Safari / iOS?▾
ffmpeg.wasm requires SharedArrayBuffer with the right HTTP headers. Chrome and Edge are most reliable; Safari can be hit-or-miss depending on version.
Can I batch-compress a folder?▾
Not yet — this tool is one file at a time. For batch jobs, run desktop ffmpeg or queue files manually.

Explore the category

Audio Format Converter Convert audio between MP3, WAV, OGG, M4A and FLAC in your browser. Choose bitrate or sample rate, then download. Runs locally via ffmpeg.wasm — no uploads. Audio Merger Concatenate multiple MP3, WAV, M4A, OGG or FLAC files into one continuous audio track. Drag to reorder, set output format and bitrate, then download. Audio Reverser Reverse any audio file so it plays backwards. Drop MP3, WAV, M4A, OGG or FLAC, choose output format, and download. ffmpeg.wasm areverse — no upload. Audio Loudness Normalizer (LUFS) Normalize loudness of MP3, WAV, M4A, OGG and FLAC files using ffmpeg loudnorm (EBU R128). Hit Spotify, podcast or broadcast targets — runs locally via ffmpeg.wasm. Audio Speed & Pitch Changer Speed audio up or slow it down without changing pitch, or shift pitch in semitones independently of speed. MP3, WAV, M4A, OGG, FLAC. ffmpeg.wasm in browser. MP3 Cutter & Audio Trimmer Trim MP3, WAV, M4A and OGG audio with a visual waveform editor. Set start and end with sliders, preview the selection, then download.
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Glossary

Bitrate
Kilobits per second of audio data. Lower bitrate = smaller file but lower fidelity.
Lossy compression
Encoding that discards inaudible (or barely audible) detail to shrink the file. MP3, OGG Vorbis, AAC are all lossy.
MP3 (libmp3lame)
The most compatible lossy audio codec. Used here via the LAME encoder built into ffmpeg.
OGG Vorbis
An open-source lossy codec that typically sounds better than MP3 at the same bitrate.
AAC / M4A
Advanced Audio Coding wrapped in an MP4 audio container. Default on Apple devices, generally beats MP3 below 128 kbps.
ffmpeg.wasm
Browser-side WebAssembly build of ffmpeg, used here to perform the re-encoding without a server.