MP3Gain

MP3Gain 2026 is an updated build of the original MP3Gain program.
It adds Unicode support, 64-bit, and compatibility with current Windows versions.

The newest build also supports parallel processing, so expect your CPU to get warm if you have a large collection of files.

You can apply non-destructive volume normalization to MP3 files.
It uses ReplayGain to adjust the volume of MP3 files so that they have the same perceived loudness.