Start with a copy
Keep the original recording. Export or process a duplicate so you can compare the result and return to the source if the change sounds worse.
Choose what you are normalizing
Peak normalization scales the highest sample to a target. Loudness normalization targets a measured listening level. They solve different problems, so a peak-normalized file can still be much quieter than another recording.
Use integrated loudness for overall level and peak readings for headroom. If the file already has clipped samples, normalization does not reconstruct them.
Check the delivered file
Measure after export, particularly when converting to a lossy format. Listen for distortion and compare at matched playback levels rather than assuming louder is better.
- Measure the source with the LUFS meter.
- Normalize a copy.
- Measure the downloaded output.
- Listen to loud words, music transitions and quiet passages.