stripe.com↗

CSS and JavaScript in the critical path delay first paint — visitors stare at a blank screen, and Largest Contentful Paint (a Google ranking signal) suffers.

Impact — Largest Contentful Paint is a Google ranking signal. Sites in the slowest quartile of their category see 30–50% less organic search traffic than faster peers.

Third-party code — tag managers, analytics, chat widgets, ad pixels — runs on every page and is a leading cause of slow, janky sites. It also changes without warning, outside your control.

Impact — Third-party scripts cause ~57% of JavaScript-related main-thread delays on a typical site (Web Almanac). They also change without warning, outside your control.

Large scripts block the browser’s main thread, so the page looks loaded but does not respond to taps or clicks. This is the most common cause of a slow mobile experience and directly drives up bounce rate.

Impact — Heavy JavaScript is the #1 driver of slow mobile sites — 53% of mobile users abandon pages that take longer than 3 seconds to load (Google mobile-speed research).

Accessibility issues exclude users of assistive technology and create legal exposure (ADA / European Accessibility Act). Many fixes also help SEO.

Impact — About 15% of users have a disability (WHO). Accessibility gaps both exclude these users and create ADA/EAA compliance risk in the US and EU.

These are not training bots — they are the live retrieval crawlers ChatGPT search, Perplexity and Claude use to read a page before citing it in an answer. Blocking them removes the site from AI answers entirely, while training opt-outs (GPTBot, CCBot…) can stay blocked with no citation impact.

Impact — Buyers increasingly ask ChatGPT, Perplexity and Claude for recommendations. A site these crawlers cannot read cannot be cited — the traffic goes to a competitor whose site they can.

User-agent: OAI-SearchBot
Allow: /

User-agent: ChatGPT-User
Allow: /

User-agent: Claude-User
Allow: /

User-agent: PerplexityBot
Allow: /

User-agent: Perplexity-User
Allow: /

If search engines cannot follow your links or understand their text, pages will not be discovered or rank — directly capping organic traffic.

Impact — Crawlability issues directly cap organic search traffic. Search engines cannot rank what they cannot follow or understand.

Oversized images waste bandwidth and slow the largest element on the page. On mobile connections this is often the single biggest load-time cost.

Impact — Images account for roughly 25% of an average mobile page (HTTP Archive). Every MB of unoptimized images adds 1–2 seconds of mobile load time.

Schema.org JSON-LD tells search engines and answer engines what each page is — an Organization, an Article, a Product, an FAQ. Pages with structured data earn richer search results and are easier for LLMs to summarize and cite accurately.

Impact — Structured data is a low-risk SEO and AI-visibility win: it doesn’t change your design but materially improves how engines understand and present your pages.

<script type="application/ld+json">
{
  "@context": "https://schema.org",
  "@type": "Organization",
  "name": "stripe.com",
  "url": "https://stripe.com",
  "logo": "https://stripe.com/logo.png",
  "sameAs": [
    "https://www.linkedin.com/company/your-company",
    "https://twitter.com/your-handle"
  ]
}
</script>

Without long cache headers, repeat visitors re-download assets that never changed — slower return visits and wasted bandwidth.

Impact — Returning visitors slow their own experience without caching. Small fix, compounding gain: every repeat visit benefits.

Heavy pages cost real money for users on metered mobile data and load slowly on weak connections — a meaningful share of every site’s traffic.

Impact — Every additional megabyte of page weight typically adds 1–2 seconds of mobile load time on a slow connection (HTTP Archive).