Audio Compressor: Reduce MP3, WAV & FLAC Size Free Online, No Upload

About the Audio Compressor

Audio compression works by re-encoding a file at a lower bitrate, throwing away audio detail your ear is least likely to notice and replacing the original stream with a smaller one. This tool runs that re-encode through FFmpeg compiled to WebAssembly, right inside your browser tab, so your files never leave your device. Pick a quality preset, pick an output format, and compress a single file or a whole batch at once.

Choosing a quality preset

High Quality targets 192 kbps and stays transparent to most ears on typical headphones and speakers, a safe choice when you are not sure how much you can afford to lose. Balanced drops to 128 kbps, the bitrate most streaming services settled on years ago because it holds up well for casual listening while cutting file size close to a third from an uncompressed source. Small File goes down to 96 kbps, where compression artifacts become noticeable on complex music but stay unobtrusive for most other content. Tiny compresses to 64 kbps, built for voice recordings and podcasts where intelligibility matters far more than musical fidelity, and where the bitrate drop yields the biggest file size win of the four presets.

Picking an output format

MP3 plays on nearly every device and app ever made, which makes it the default choice when you do not know where the file is headed next. AAC squeezes better quality out of the same bitrate, a real advantage if the audio is going into a modern app or platform rather than an old MP3 player. OGG uses the open-source Vorbis codec and tends to compress a little more efficiently than MP3 at comparable quality, a fit for web projects and open pipelines that already lean on open formats. All three options run through the same encoder settings for a given preset, so the format choice is about where the file needs to play, not how aggressively it gets shrunk.

Single files versus batch

The Single tab handles one file at a time and shows you the exact before-and-after size along with the percentage saved once the job finishes. Switch to the Batch tab to drop in several files at once, apply one preset and format to the whole group, and let them process one after another while you watch each item's status update in the queue. Batch mode is built for situations like compressing an entire folder of voice memos or a whole album at once, where clicking through the single-file flow repeatedly would waste time. Both tabs use the same FFmpeg engine underneath, so results are identical whichever path you take.

Getting the best size-to-quality tradeoff

Start from the highest-quality source file you have, ideally a WAV or FLAC rather than an MP3 that has already been compressed once. Re-encoding a file that is already lossy stacks a second round of compression artifacts on top of the first, a problem known as generation loss, and the result usually sounds worse than compressing the original source directly at the same target bitrate. If you are unsure which preset to pick, start with Balanced and listen back on the device you plan to use, since artifacts that are obvious on studio headphones often disappear entirely on a phone speaker or in a car.

Common use cases

Podcasters compress finished episodes down before uploading to a host with strict size limits. Musicians shrink a full-quality mix down to a shareable size for quick feedback from collaborators. People with large voice memo libraries batch-compress everything down to the Tiny preset to reclaim storage space without losing the ability to understand what was recorded. In every case the tradeoff is the same: lower bitrate means smaller files and a small, often inaudible, loss of fidelity.

What happens during processing

The FFmpeg engine, about 32 MB, downloads once and gets cached by your browser, so it only slows down the very first job you run. After that, compressing a file strips any video track if one happens to be attached, decodes the audio, and re-encodes it at the target bitrate and codec you selected, all on your own CPU rather than a remote server. Larger files and lower bitrates both take longer to process since there is more audio data to work through, and a progress bar tracks the job so you know it is still running rather than stalled. Closing the tab mid-compression cancels the job, so leave it open until the download button appears.

Related: Audio Clipper to trim files before compressing, or Audio Converter to change format.

Frequently Asked Questions