Statement
Critical CSS delivery shall use a preload/swap pattern (link rel="preload" as="style" with onload swap) rather than build-time CSS inlining tools, avoiding complex build-time CSS parsing dependencies while maintaining above-the-fold rendering performance.
Rationale
Critters was removed due to build-time parsing complexity and compatibility issues. Preload/swap achieves comparable results with simpler tooling. Delivered by WP-D1 (D-D1-02).
Notes
Deprecated: preload/swap pattern reverted in d150f190. Caused CLS regression (0.521) with no FCP/LCP benefit — same-origin CSS was already discovered by the browser's speculative preload scanner. Blocking CSS delivery restored as the correct contract.
Topics
Owner: rendering-runtime
Applies To
- Architecture DOC-00020