This rules triggers when PageSpeed Insights detects that the size of one of your resources could be reduced through minification.
Minification refers to the process of removing unnecessary or redundant data without affecting how the resource is processed by the browser - e.g. code comments and formatting, removing unused code, using shorter variable and function names, and so on.
See preprocessing & context-specific optimizations to learn more.
- To minify HTML, try HTMLMinifier
- To minify CSS, try CSSNano and csso.
Alternatively, the PageSpeed Module, integrates with with an Apache or Nginx web server to automatically optimize your site, including resource minification.