Cloudflare
Cloudflare is a web-infrastructure and website-security company, providing content-delivery-network services, DDoS mitigation, Internet security, and distributed domain-name-server services.
What detecting Cloudflare tells you about a site
Cloudflare sits in front of the origin as CDN, DNS and security layer, and it is one of the most reliably detectable technologies on the web. The signature is the cf-ray response header (a unique edge-request ID), a Server: cloudflare line, and frequently a __cf_bm bot-management cookie. Its near-ubiquity makes it a weak signal of team identity but a useful one operationally: the origin is shielded behind Cloudflare's edge, its real IP is hidden, and the site benefits from caching, WAF and DDoS protection by default. It spans everything from hobby blogs to large platforms.
The detail that matters for Cloudflare
Extra Cloudflare products leave their own marks — a cf-cache-status header reveals edge caching behaviour, and headers or challenge pages from Turnstile, Workers or Cloudflare Access tell you the team has gone beyond the free proxy into its application platform.
Cloudflare in a real-world stack
When you find Cloudflare, it rarely travels alone. Fronts any origin stack imaginable; increasingly paired with Cloudflare's own Workers/Pages, R2 storage and D1 when the team commits to the platform.
About
Cloudflare is a web-infrastructure and website-security company, providing content-delivery-network services, DDoS mitigation, Internet security, and distributed domain-name-server services.
Categories: CDN
Quick facts
Detection methodology for CDN
CDN detection runs against response headers (`cf-ray` for Cloudflare, `x-amz-cf-id` for CloudFront, `x-served-by` for Fastly, `x-cache` for Akamai) and asset hostnames in the page's resource tree. The same site can sit behind multiple CDNs (an edge cache in front of an origin CDN); we surface each one separately so the layered architecture is visible.
How we detect Cloudflare
Sourcemap Explorer carries 7 fingerprint signals for Cloudflare, spread across 5 channels — response header, cookie, meta tag, javascript global and dom selector. The exact patterns are listed below, and you can replay each one in Chrome DevTools to confirm a match by hand.
Each signal alone is rarely conclusive — Sourcemap Explorer cross-references all of them and weights by confidence. You can reproduce any of these checks yourself in Chrome DevTools.
Server-side fingerprint: the response header reveals the technology behind the page. Visible in DevTools → Network → response headers.
Server: ^cloudflare$
cf-cache-status:
cf-ray:
Cookies set by the platform. Visible in DevTools → Application → Cookies.
__cfduid
<meta> tag injected into the document. Visible by viewing the page source.
<meta name="image" content="//cdn\.cloudflare">
Window-level global the technology installs on page. Reproducible by typing the path into the DevTools console.
window.CloudFlare
A DOM selector that only this technology's pages render. Verified at runtime by the content script.
img[src*='//cdn.cloudflare']
FAQ
How do I check if a website is using Cloudflare?
Open the page in Chrome, click the Sourcemap Explorer toolbar icon, and read the Stack tab. Cloudflare's specific fingerprints here are response header, cookie, meta tag, javascript global and dom selector, and the popup flags Cloudflare whenever any combination of them is found. The same checks can be reproduced manually in DevTools — see the "How we detect" section above.
What Cloudflare version can Sourcemap Explorer detect?
Cloudflare ships as a hosted cdn rather than a bundled npm package, so version-specific detection isn't always possible. Where the platform leaks a version in response headers (`X-Powered-By`, `Server`, generator meta tags) we surface it; otherwise we report presence only.
Where can I read more about Cloudflare?
Official site: https://www.cloudflare.com. For Sourcemap Explorer's detection guide, see the deep-dive link below or the related guides in the cross-link section.
Keep reading on Sourcemap Explorer
Practical guides
Alternative tools
Detected by Sourcemap Explorer
Open the popup on any page running Cloudflareand you'll see the exact version pulled from the bundled package.json when sourcemaps are exposed.