WordPress v6.3.1 inlines styles for used blocks via the wp_head
hook. However there is an additional wrinkle. If the SCRIPT_DEBUG
constant is set and truthy, then a minimized copy of the styles will be inlined. The minimized copy is pre-generated and included with WordPress.
Code for choosing to use the min variant is in wp-includes/blocks.php:
// Check whether styles should have a ".min" suffix or not.
$suffix = SCRIPT_DEBUG ? '' : '.min';
if ( $is_core_block ) {
$style_path = ( 'editorStyle' === $field_name ) ? "editor{$suffix}.css" : "style{$suffix}.css";
}
Minimized styles can be found in the source listings of each block in wp-includes/blocks/, look for pairs of files with .css and .min.css extensions.
The scripts themselves are enqueued from the Block::render
method of wp-includes/class-wp-block.php.