BYHS Standard v1.0

BYHS Engineering Standards

Baseline ratified July 2026 · Every production website is built and audited to this standard. Future revisions graduate from lab research per the methodology.

Performance

Core Web Vitals budget tighter than Google's thresholds: LCP ≤ 1.8 s, CLS ≤ 0.05, INP ≤ 150 ms on mid-range mobile (rationale).
Static or server-rendered HTML — meaningful content in the initial response, always.
Compressed total JavaScript ≤ 75 KB; scripts deferred; no render-blocking third parties.
Images sized, compressed (WebP/AVIF), with explicit dimensions; hero image ≤ 150 KB with fetchpriority="high".
Fonts self-hosted, preloaded, font-display: swap.
Long-cache immutable assets; HTML uncached or short-cached at the edge.

Technical SEO

One canonical URL form; every variant 301s to it in a single hop; self-referencing canonical tags on every page (rationale).
Unique title and meta description per page; one H1; ordered heading hierarchy.
XML sitemap containing only canonical, 200-status URLs; honest lastmod dates.
Deliberate robots policy: production sites open to search and AI crawlers; demos and staging explicitly blocked.
Every page reachable within three clicks via plain anchor links; zero internal redirects or broken links at ship time.
Correct response codes — no soft 404s, no 200 error pages.

Structured data

JSON-LD only; entities anchored with stable @ids (rationale).
Organization sitewide; most-specific LocalBusiness subtype with NAP matching Google Business Profile exactly; BreadcrumbList mirroring visible navigation.
Nothing in schema that isn't visible on the page. No self-serving review markup.
Validated (Rich Results Test + Schema.org validator) on every deploy; enhancement reports monitored in Search Console.

Accessibility

WCAG 2.2 AA (rationale): 4.5:1 body-text contrast enforced at the design-token level.
Semantic landmarks and native elements first; ARIA only as repair.
Full keyboard operability with visible focus; alt text on all informative images.
All motion behind prefers-reduced-motion.

AI search readiness

Fact-dense, semantically structured HTML that assistants can parse without JavaScript (rationale).
Business facts (hours, service area, contact) stated in extractable prose, consistent with structured data.
AI crawler access deliberately configured per property, with crawler activity logged and reviewed.

Security & delivery

HTTPS everywhere; zero mixed content.
Security headers on every response: X-Content-Type-Options, X-Frame-Options/frame-ancestors, Referrer-Policy, Permissions-Policy.
Served from a global edge network with brotli/gzip compression.

This page is the living summary. Each revision will be versioned, dated, and justified by a published experiment — if a line changes, there will be a paper trail explaining why.