When a user visits a website, their browser downloads HTML, CSS, JavaScript, images, and fonts from the origin server. If that server is located far away, every asset travels across the globe, adding hundreds of milliseconds to every request.
A CDN solves this by caching copies of static assets at edge nodes distributed around the world. The user is served from the nearest edge node, often cutting latency dramatically.
Why it matters for SEO: Page speed is a ranking factor. CDNs are one of the most cost-effective ways to reduce Time to First Byte (TTFB) and Largest Contentful Paint (LCP), both of which affect Core Web Vitals scores.
What SearchVitals checks: The Architecture audit detects whether a CDN is in use by examining response headers for CDN signatures (Cloudflare, Fastly, AWS CloudFront, Akamai, etc.). Sites serving all assets from origin are flagged as a high-priority finding.