Minification consists of reducing as much as possible a volume of data and therefore the weight of the carrying file by removing elements that the reading machine can do without (typically: spaces, line breaks and comments). CSS style sheets can be minified.
Objectives
Minimize the amount of data to download
Improve performance
Reduce the energy impact linked to consulting the digital book
Implementation
Remove unnecessary spaces and comments in CSS files using dedicated tools.
Control
Manually check within all CSS files that no line returns, comments, indentations or line breaks are present.
Or identify the list of non-minified CSS files using development tools (browsers , online tools, etc.)