Audio Compressor
Shrink oversized recordings, music, and podcasts to fit WeChat sending limits, email attachment caps, and cloud storage upload limits
Pick the bitrate that fits your needs
64kbps works well for voice and podcasts, 128kbps is the general recommendation, and 256kbps is reserved for music where audio quality matters
Preview before you download
The results panel shows a before-and-after size comparison and compression ratio, and you can listen right away to confirm the quality still holds up
Processed locally, no upload
Audio is decoded and re-encoded entirely in your browser — files never leave your device, and there's no limit on size or number of uses
Use Cases
- Meeting, class, and interview recordings from your phone can easily run into the hundreds of megabytes — compress them first so you can actually send them over WeChat or email
- Compress podcasts and audio content to the bitrate a platform requires before uploading, to avoid upload failures or forced re-transcoding
- When phone storage is running low, compressing a batch of lossless music files to MP3 can free up a lot of space
- Compress background audio and notification sounds on web pages and mini programs to a low bitrate for faster loading and less data usage
What determines an audio file's size?
An audio file's size is determined almost entirely by its bitrate: size ≈ bitrate × duration. For a 10-minute audio clip, 320kbps is about 24MB, 128kbps about 9.6MB, and 64kbps just 4.8MB. Lossless formats like WAV and FLAC skip lossy compression entirely and use a much higher bitrate (WAV is typically 1411kbps), which is why they benefit the most from compression.
This tool uses WebCodecs to decode the original audio in your browser, then re-encodes it as MP3 at the bitrate you choose. Since re-encoding is lossy and irreversible, it's best to keep the original file. If you want to try a different preset on the same file, just switch presets and compress again — everything runs locally, with no data usage.
Related audio tools
If what you actually need to compress is a video file, use Video Compressor; to keep only the audio, use Extract Audio from Video to pull out the audio track first, then come back here to compress it. Need to change format rather than shrink size? Try WAV to MP3 or M4A to MP3. To trim out just a section, use Audio Trimmer.
Frequently Asked Questions
How small can audio actually get compressed?
It depends on the original bitrate. A 320kbps MP3 compressed to 128kbps drops to roughly 40% of its original size; at 64kbps, about 20%. Lossless formats shrink even more dramatically — WAV is typically 1411kbps, so compressing it to 128kbps leaves less than 10% of the original size. A one-hour recording can go from 600MB down to around 55MB.
Does compression reduce audio quality?
Yes. MP3 is a lossy format, so the lower the bitrate, the greater the quality loss — and it's irreversible. Re-encoding a compressed file back to a higher bitrate won't restore the original quality, so it's best to keep the original file. In practice, voice recordings, podcasts, and lecture audio hold up fine even at 64kbps; for music, aim for at least 128kbps, or 256kbps if you're picky about audio quality.
How do I compress a recording to a size WeChat can send?
WeChat's file transfer limit is 100MB (200MB on some versions). A one-hour phone recording in WAV format is often several hundred megabytes — compress it with the "Standard 128kbps" preset and it'll usually land around 55MB, small enough to send directly. For meetings or lectures that are mostly speech, the "Smallest size 64kbps" preset can get it down to around 28MB with barely any noticeable quality loss.
Why didn't the file get any smaller after compression?
If the original file's bitrate is already lower than the preset you picked (say, a 96kbps MP3 with the 256kbps preset selected), re-encoding will only inflate the file, not shrink it. In that case, just switch to a lower preset. Also keep in mind that re-encoding can't restore quality that's already been lost, so converting a low-bitrate file to a higher bitrate serves no purpose.
Which formats are supported, and what's the output format?
Input supports common audio formats including MP3, M4A, WAV, FLAC, OGG, and AAC. Output is always MP3 — the most widely compatible lossy format, playable directly on phones, car stereos, media players, and virtually every platform. If you need a different output format, use the audio format converter on this site.
Are audio files uploaded to a server?
No. Decoding and re-encoding happen entirely in your browser — your audio files never leave your device or get uploaded to any server, so there's no limit on file size or number of uses.