CSS @import chains on React sites

Sites with no @import rules CSS @import rules have a good LCP most often: 80%, against 79% of all React sites. Sites with CSS @import CSS @import have it least often, at 67%.

No @import rules is the most used: 96.1% of React sites.

Across the four LCP sub-parts in Chrome's field data, the largest gap between no @import rules and CSS @import sits in time to first byte (TTFB): 696 ms median for no @import rules against 773 ms for CSS @import. Overall median field LCP is 1.6s for no @import rules (TTFB 696 ms, load delay 413 ms, load duration 144 ms, render delay 189 ms) versus 1.8s for CSS @import.

Wix sets the CSS @import rules to no @import rules on 99% of its sites, and 92% of Wix sites have a good LCP, against 79% of all sites.

PlatformCSS @import rules on its sitesGood LCP

All React sites 9,570 sitesNo @import rules 96%79%

Wix 5,824 sitesNo @import rules 99%92%

WordPress 2,342 sitesNo @import rules 96%66%

No @import rules Uses CSS @import

Does the platform explain the CSS @import rules difference?

On WordPress, 67% of sites with no @import rules CSS @import rules have a good LCP, against 46% of WordPress sites with CSS @import. Within WordPress, sites with no @import rules have a good LCP more often.

Why CSS @import defeats the browser preload scanner

Every external stylesheet blocks rendering by default, but <link rel="stylesheet"> tags are visible in the initial HTML markup so the preload scanner fetches them in parallel. @import hides dependencies inside CSS files: the browser must download the parent stylesheet, parse its rules, and only then open a second request for the imported file. Across 9,199 sites (96.1%) without @import, good LCP reaches 80% (1.5s median), while the 371 sites (3.9%) using @import record 67% good LCP (1.8s median).