MP3Gain Express

MP3Gain Express brings the MP3Gain and AACGain utilities to macOS, allowing users to analyze and adjust the playback volume of MP3 and AAC files without re‑encoding. The interface mirrors the Windows version of MP3Gain, offering a familiar workflow: select files, set a target loudness, and apply gain directly to the audio data. It can also write volume information to tags for players that read ReplayGain, and it provides an undo function to restore the original volume when possible.

The application targets macOS users who need to normalize the loudness of large music libraries, especially when files have inconsistent levels across tracks. By modifying the audio data in place, it avoids the quality loss associated with re‑encoding, while also offering a clipping‑prevention option to keep audio within safe limits.

MP3Gain Express runs on OS X 10.11 (El Capitan) or later and is distributed as a standalone zip archive. It is a stable, core macOS release that re‑introduces AAC support after a previous omission.