CDN Check
Detect CDN usage and identify the provider for any domain.
Determines whether a hostname is served through a CDN, and which one. We combine signals from
DNS (CNAME patterns, IP ranges, ASN), HTTP response headers (
via,
x-cache, cf-ray, x-amz-cf-id, x-served-by),
and known provider prefix lists. Useful for competitive analysis, debugging CDN-specific
issues, or just figuring out who hosts what.
Checking...
What we look at
- CNAME chain — patterns like
*.cloudfront.net,*.fastly.net,*.akamaiedge.net,*.azureedge.netare dead giveaways. - IP / ASN — the resolved IP's ASN often identifies a CDN even when DNS hides it (AS13335 = Cloudflare, AS16509 / AS14618 = Amazon, AS54113 = Fastly, AS20940 = Akamai).
- Response headers — CDNs reliably set telltale headers:
cf-ray,x-amz-cf-id,x-served-by,x-cache,fastly-debug-state, etc.
Common use cases
- Competitive analysis — see what CDN a competitor uses and infer their scale and infrastructure choices.
- Debugging CDN-specific issues — Cloudflare 522 errors mean origin unreachable; Fastly 503 typically means a service config issue. Knowing the CDN narrows the diagnosis.
- Verifying your own CDN setup — confirm your domain is actually being fronted by the CDN you expect (a misconfigured DNS can quietly bypass it).
- Picking a CDN — see which CDN the high-traffic sites in your industry chose; it's a reasonable starting point for shortlisting.
Limitations
- Some companies build their own private CDN (Apple, Netflix, large enterprises). We'll typically classify those as "unknown / private" since they don't match public-provider signals.
- A single domain can use different CDNs for different paths (one for HTML, another for images/video). We check the apex; sub-resources may differ.
- Headers from HTTP Header check give you the most authoritative live signal for any individual request.