Hopefully, some background information on this aspect of the mastering process will leave you better able to make the right decisions for your project. However, many are unaware of the major tradeoffs in sonic quality introduced in the quest to be the loudest track on the shuffle playlist.
The tendency to try and make CDs as loud as possible in the mastering stage (and increasingly even during mixing) has become so common that it’s viewed by many people today as what “mastering” is. One of the most contentious issues in CD mastering these days is relative loudness.