Fastly
Fastly is a cloud computing services provider. Fastly's cloud platform provides a content delivery network, Internet security services, load balancing, and video & streaming services.
About
Fastly is a cloud computing services provider. Fastly's cloud platform provides a content delivery network, Internet security services, load balancing, and video & streaming 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 Fastly
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.
Fastly-Debug-Digest:
Vary: Fastly-SSL
X-Fastly-Request-ID:
server: Fastly
x-fastly-origin:
x-fastly-request-id:
x-via-fastly:
FAQ
How do I check if a website is using Fastly?
Open the page in Chrome, click the Sourcemap Explorer toolbar icon, and read the Stack tab. The popup matches Fastly's fingerprint signals (response headers, asset URL prefixes, runtime globals, sourcemap paths) and flags it whenever any combination is found. The same checks can be reproduced manually in DevTools — see the "How we detect" section above.
What Fastly version can Sourcemap Explorer detect?
Fastly 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.
How much does Fastly cost?
Fastly's pricing model is documented as: payg. Detection is independent of the pricing tier — Sourcemap Explorer flags the technology by its fingerprints, regardless of which paid plan a site is on. See the official site for the current pricing page.
Where can I read more about Fastly?
Official site: https://www.fastly.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 Fastlyand you'll see the exact version pulled from the bundled package.json when sourcemaps are exposed.