Google hard gate — `robots.txt` Disallow blocks crawling AND blocks rendering of JS/CSS; "Google Search won't render JavaScript from blocked files or on blocked pages"

Claim: A Disallow in robots.txt blocks crawling of matching URLs. Crucially, it also blocks rendering of any JS/CSS files referenced from a page — Google states directly: "Google Search won't render JavaScript from blocked files or on blocked pages."

Practical implication: a robots.txt that disallows /wp-content/ or /assets/ (a common WordPress / theme-developer mistake) can break rendering of pages that depend on those assets, with no error in Search Console beyond degraded rendered HTML in URL Inspection.

Note also: blocked URLs can still be indexed URL-only (no snippet, no content) if they're externally linked. So robots.txt is not a way to hide pages from the index — only noindex does that, and noindex requires Google to be able to fetch the page to see the directive.

Source: Google Search Central robots.txt documentation; JavaScript SEO docs.

Confidence: Verified. Grade A.

Caveat: Cross-link to the lifecycle brief's reachability gate at Google robots.txt 5xx response postpones the whole crawl — Google will not guess; DNS/server reachability is a hard gate on the entire pipeline for the 5xx-on-robots failure mode.