A Content Delivery Network caches your content on servers around the world so visitors download from a nearby location instead of your origin server. CDNs cut latency, absorb traffic spikes, and add DDoS protection. Almost any site with a global or growing audience benefits from one.

It reads the HTTP response headers the server returns and matches known fingerprints: cf-ray and the server value 'cloudflare' for Cloudflare, x-amz-cf-id for CloudFront, x-served-by and x-fastly for Fastly, x-vercel-id for Vercel, x-akamai for Akamai, and several others. These headers are reliable signals because CDNs add them automatically.

Some CDNs can be configured to strip identifying headers for privacy or security. Others only add fingerprints on cached responses, so a first uncached hit may look like the origin. The tool reports what the headers reveal; absence of a known fingerprint is not absolute proof there is no CDN.

Yes, indirectly. CDNs improve Time to First Byte and overall load speed, both of which feed into Core Web Vitals and Google's page experience signals. Faster pages also reduce bounce rate and improve crawl efficiency, since Googlebot can fetch more pages in the same crawl budget.

Yes. Large sites sometimes layer CDNs (multi-CDN) for redundancy and performance, or use one CDN for the HTML and another for static assets and images. The headers on the HTML response reflect whichever CDN served that specific document, which is what this tool reports.

The clearest signals are the 'cf-ray' header (a unique Cloudflare request ID) and a 'server' header value of 'cloudflare'. The 'cf-cache-status' header also appears on cacheable responses. Any of these confirm the site is proxied through Cloudflare.

No. DNS lookups can hint at a CDN via CNAME records, but they can be misleading. This tool inspects the live HTTP response headers from the actual page request, which is a more direct and accurate way to confirm which CDN is serving the content right now.