A Content Delivery Network is a global network of edge servers that cache and serve your site's assets from the location nearest the user. Instead of every visitor connecting to your single origin server, they hit the closest edge POP and get a sub-30 ms response.

Do I need a CDN if my site is fast already?

Almost always yes. Even fast origins add 100-800 ms of latency for visitors far away, and a CDN also handles HTTPS termination, HTTP/3, DDoS protection and bandwidth offload. Most modern CDN tiers cost less than the bandwidth savings they generate.

Which CDN should I use?

Cloudflare and Fastly are the most popular general-purpose choices in 2026 with strong free / low-cost tiers and excellent global coverage. Vercel and Netlify bundle a CDN with their hosting. AWS CloudFront integrates with the broader AWS ecosystem. The right choice depends on integration with your existing stack and whether you need image optimisation, edge functions or specific compliance regions.

Does a CDN affect SEO directly?

Yes. Faster load times improve every Core Web Vital that Google measures, particularly Largest Contentful Paint and Time to First Byte. Better real-user metrics in Chrome User Experience Report (CrUX) feed directly into Google's page-experience ranking signal.

How do I tell if my CDN cache is working?

Run this test twice. The first request may be a MISS (the edge fetches from origin); the second should be a HIT (served from the edge cache). If you only ever see MISS or DYNAMIC, your Cache-Control headers are preventing caching and the CDN is providing far less value than it could.

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CDN Usage Test

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The CDN Usage Test detects whether your website is being served through a Content Delivery Network (CDN) and identifies exactly which provider — Cloudflare, Fastly, AWS CloudFront, Akamai, Google Cloud CDN, Azure Front Door or one of the smaller specialised players. We inspect response headers, server signatures, IP-range registrations and cache-status indicators to give a definitive answer plus a real-time view of edge cache performance, the geographic location serving the request, HTTP/2-or-3 negotiation, and TLS termination at the edge. Without a CDN, every visitor on every continent waits for a round trip to your single origin server — typically adding 200-800 ms to Time to First Byte.

What This Tool Checks

CDN provider detection from response headers (CF-Ray, X-Served-By, X-Cache, X-Amz-Cf-Id, etc.)
Edge cache hit / miss / revalidate status
Geographic edge location (POP) responding to your request
HTTP/2 and HTTP/3 (QUIC) protocol support at the edge
TLS version and certificate authority
Brotli / gzip negotiated at the edge
Origin shielding indicators (multi-tier CDN architecture)
Approximate Time to First Byte vs. an origin-only baseline

Why It Matters for SEO

A CDN is the single largest performance and SEO improvement most sites can ship in one deploy. Without a CDN, every visitor waits for a round trip to your origin — 200 ms from across town, 400 ms from across the country, 800+ ms from another continent. With a CDN, static assets and (with stale-while-revalidate) HTML are served from the edge POP closest to the user, typically in 10-30 ms. That improvement compounds into faster First Contentful Paint, faster Largest Contentful Paint, lower bounce rates and measurably higher Core Web Vitals scores — all of which feed Google's page-experience ranking signal directly. CDNs also absorb DDoS and bot traffic, terminate TLS at the edge, negotiate HTTP/3, and cut origin bandwidth costs by 70-95%.

How to Fix It

Pick a CDN and put it in front of your origin (Cloudflare, Fastly, Vercel, Bunny.net and AWS CloudFront all have generous free or low-cost tiers). Point your DNS at the CDN, terminate TLS at the edge, enable Brotli and HTTP/3, then audit your Cache-Control headers so static assets cache for 1 year + immutable and anonymous HTML uses stale-while-revalidate. Re-run this test until the cache-status header shows HIT on repeat requests and the edge POP matches your visitor's region.

How It Works

We send a real GET request from our test infrastructure, parse every standard and provider-specific response header, then cross-check against published CDN IP ranges and behavioural fingerprints (e.g. CF-Ray means Cloudflare, X-Served-By plus X-Timer means Fastly, X-Amz-Cf-Pop means CloudFront). When the CDN exposes its cache state we report HIT / MISS / DYNAMIC. Edge location, protocol and compression details come from the live TCP / TLS / HTTP exchange, so the report reflects the exact path your real users see.

Common Mistakes to Avoid

Running a global e-commerce or SaaS site directly off a single origin server with no CDN
CDN is enabled but Cache-Control headers force MISS on every request (defeats the CDN entirely)
Using a CDN for static assets but routing HTML straight to origin even though pages are anonymous
Forgetting to enable Brotli / HTTP/3 at the CDN — both are usually one toggle
Origin still serving the same large hero images uncompressed because the CDN does not transform on the fly

Quick Checklist

CDN detected (Cloudflare, Fastly, CloudFront, Akamai or equivalent)
Edge cache returns HIT on repeat requests
HTTP/2 or HTTP/3 negotiated at the edge
Brotli enabled for HTML, CSS and JS
Static assets cached 1 year with immutable
Anonymous HTML uses stale-while-revalidate

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