Audio Compressor is a Firefox addon designed to improve audio levels by implementing dynamic range compression. This tool offers various presets that cater to different compression needs, allowing users to achieve more balanced sound volumes. Users can also customize the default settings or adjust them for specific websites, enhancing the overall listening experience without the need for additional software.

However, it is important to note that Audio Compressor has limitations; it may not function correctly on certain sites due to cross-origin browser security restrictions that prevent scripts from modifying audio or video from different hosts. The addon utilizes the Web Audio API, specifically the DynamicsCompressorNode, to manipulate the audio context for webpages, although it may not be compatible with every site.