Long meetings, lectures, and podcasts can produce recordings that are awkward to send or upload. Audio Compression reduces file size by targeting a lower audio bitrate, with processing performed locally in your browser.
What determines audio file size?
File size ≈ bitrate × duration. At 320 kbps, one minute of MP3 audio uses roughly 2.4 MB. At 128 kbps, it uses roughly 0.96 MB. When duration stays the same, reducing bitrate is a direct way to shrink a lossy audio file.
How the tool compresses audio
It reads the duration and estimates the source's average bitrate from file size and duration.
It calculates a target bitrate as original bitrate × quality percentage.
FFmpeg re-encodes the audio in your selected format.
A quality value of 50 therefore targets roughly half the original bitrate. Forecast shows a proportional size estimate. Actual results depend on the encoder and format; lossless or uncompressed outputs do not necessarily follow the requested bitrate.
How to compress an audio file
- Open Audio Compression and select a file.
- Choose an Output Format; the default is mp3.
- Adjust Quality, which defaults to 75, and check Forecast.
- Click Start, compare the completed size under After, and download the result.
Suggested quality settings
- Speech, meetings, lectures, and podcasts: try 30–50, then check that voices remain clear.
- Everyday music listening: try 50–75 for a balance of size and quality.
- Music where detail matters: start at 75 or above and listen carefully before reducing further.
If the source already has a low bitrate, such as a 64 kbps speech recording, aggressive compression can introduce watery sounds and distortion. Raise the quality if needed.
A note about WAV files
Typical uncompressed WAV audio has a high bitrate. Converting WAV to MP3 often saves far more space than trying to reduce the bitrate while keeping WAV. If the compressor's source-relative bitrate is unsuitable for MP3, use Audio Format Converter to convert the WAV first.
Other ways to reduce size
- Remove unnecessary silence or conversation with Audio Clip.
- If you only need a video's sound, use Extract Audio from Video instead of keeping the entire video.
Frequently asked questions
Will compression reduce audio quality?
Lossy compression discards some detail, with more noticeable effects at lower bitrates. Try a moderate setting and listen before reducing further.
Can I cancel processing?
Yes. Click Stop during conversion.
Related tools
音频剪辑与视频压缩：两个独立的浏览器端媒体工具
音频剪辑工具与视频压缩工具分别处理不同的媒体类型，页面和用途彼此独立。音频剪辑工具位于 Audio Clip，视频压缩工具位于 Video Compression。需要裁剪声音片段时使用前者，需要缩小视频文件体积时使用后者。
- 音频剪辑工具 Audio Clip：面向音频文件的片段选取与裁剪，与视频文件无关。
- 视频压缩工具 Video Compression：面向视频文件的体积压缩，与音频文件无关。
两者均在浏览器中运行，各自只处理对应的媒体类型，选择时按文件类型区分即可。
