Breaking: #107944 - Frontend CSS file processing no longer removes comments and whitespaces
See forge#107944
Description
When the TYPO3 frontend is configured to compress included CSS assets, it also tried to minify CSS by removing comments and some whitespaces.
This feature has been removed: The implementation is brittle especially with modern CSS syntax capabilities and there are typically no measurable performance gains neither when transferring files nor when clients parse files.
Impact
CSS asset files included in frontend pages may become larger when
they include many comments. TYPO3 CSS parsing was disabled by default
and only active using a reconfigured system toggle
$GLOBALS
plus additional TypoScript.
This removed feature should usually have low impact and most systems can probably ignore this change.
Affected installations
Systems actively using the CSS parsing feature in TYPO3 frontend asset management may be affected.
Migration
Instances worried about CSS asset file sizes that relied on the feature could either optimize their CSS files manually, or ignore the fact clients will receive comments, or - better - should consider establishing a specialized frontend build chain to minify CSS and probably JavaScript as well. Solutions often come with many more suitable features on this level like linting and syntax checking that TYPO3 core will never provide on its own.