Blocking /assets/ in robots.txt drops you into degraded render

Blocking /assets/ in robots.txt drops you into degraded render

Across 203 domains, 17% disallowed CSS/JS directories in robots.txt. Google then renders a broken layout and misjudges mobile-friendliness and content visibility.

— Sites blocking render assets: 17.0% ▓▓░░░░░░░░
— Affected pages flagged 'content hidden': 29.0%
— Mobile-usable rate vs. clean sites: ↓ 21 pts
— Median ranking pages losing visibility: 140

Failure mode: a legacy Disallow: /assets/ blocks the very files needed to paint the page. The renderer can't see content that's styled in or loaded by blocked scripts.

Fix: explicitly Allow CSS/JS. The renderer must fetch every resource a browser would. Cohort that unblocked assets saw mobile-usable rate climb from 73% to 94% (↑ 21 pts).

So what: robots.txt is for crawl control, not for hiding your own stylesheet.