Content Delivery Networks (CDNs) are a core part of modern web infrastructure. They cache and serve website content from edge locations around the world, reducing latency and improving performance. Knowing which CDN a website uses is valuable for performance benchmarking, competitive analysis, infrastructure planning, and sales prospecting if you work in the CDN or web performance space.
HTTP Header-Based Detection
The most reliable way to detect a CDN is by inspecting HTTP response headers. Most CDNs add distinctive headers to every response:
- Cloudflare: The
Server: cloudflareheader andcf-rayheader are unmistakable. Cloudflare also setscf-cache-statusto indicate cache hit/miss status. - Fastly: Look for
X-Served-Byheaders containing Fastly cache node identifiers, andX-CacheorX-Cache-Hitsheaders. - Akamai: The
X-Akamai-Transformedheader and edge server identifiers inX-True-Cache-Keyconfirm Akamai. - AWS CloudFront: The
X-Amz-Cf-IdandX-Amz-Cf-Popheaders, plusViaheaders containingcloudfront, identify Amazon's CDN. - Vercel: The
X-Vercel-Idheader andServer: Vercelidentify Vercel's edge network.
DNS-Based CDN Detection
DNS records often reveal CDN usage before you even load the page. CNAME records frequently point to CDN-specific domains:
*.cloudflare.comor Cloudflare IP ranges*.fastly.netfor Fastly*.cloudfront.netfor AWS CloudFront*.akamaiedge.netor*.akamaized.netfor Akamai
Running a dig or nslookup on the domain and following the CNAME chain reveals the CDN layer without making an HTTP request.
Why CDN Detection Matters
CDN choice directly affects website performance. Cloudflare offers integrated security and DDoS protection. Fastly is known for real-time configuration updates. AWS CloudFront integrates tightly with the AWS ecosystem. Understanding which CDN a competitor uses helps you benchmark your own performance and make informed infrastructure decisions.
Automated CDN Detection
WhatStack combines HTTP header analysis, DNS record inspection, and IP range matching to detect CDNs with high accuracy. The scan distinguishes between the CDN layer and the origin hosting provider, so you see the full infrastructure picture. Try the WhatStack scanner on any website to see its CDN and complete technology stack.