CDN
A distributed network that serves content near clients and absorbs traffic from the origin.
What CDN means
It improves delivery but can preserve stale, transformed, or client-specific variants.
Where CDN comes up on this site
- Do AI crawlers and agents render JavaScript?Each file looked like HTML and was not: a template with bindings and a 69 KB client-side runtime that fetched React from a CDN and then re-read the page’s own URL to find the resources it expected.
- How to write an llms.txt, and how to check it is actually being servedA CDN that cached the 404 from before the file existed will keep serving it after you publish.
- How to audit an XML sitemap: status, content type, canonical URLs and stale entriesThe redirect in front of it is uncached at both the CDN and the origin's page cache, so every request for the conventional path pays a full origin round trip: 954, 1,562 and 1,138 milliseconds on three consecutive scans .
- HTTP status codes for crawlers: what a 200 can hide, when a 403 is not a block, and the one control that tells them apartThe headers that expose this are the cache-status header the CDN adds and the age of the object, read against the validators the origin sent.
- Cached robots.txt and llms.txt: stale, split, or blockedrobots.txt, llms.txt, sitemap.xml and an entity map are small files that change rarely, which is exactly the profile a CDN caches hardest.
Terms this definition uses
Definitions that name CDN
Edge transformation · Origin server · Edge node · 502 response · Edge redirect · edge cache
Related terms in HTTP, edge and rendering
The delivery layer between an origin and a client: proxies, caches, redirects, status codes and the headers that decide what a crawler actually received.
Origin server · Reverse proxy · Edge node · WAF · Bot score · TLS handshake · DNS resolution · DNS timeout · Connection timeout · Read timeout · Redirect chain · Redirect loop · 301 redirect · 302 redirect · 307 redirect · 308 redirect · 304 response · 404 response · 410 response · 429 response · 500 response · 502 response · 503 response · 504 response · HEAD request · GET request · Content type · MIME sniffing · Content encoding · Compression · Brotli · ETag · Last-Modified · If-None-Match · Cache hit · Cache miss · Cache key · Vary header · Stale response · Stale-while-revalidate · Edge redirect · Origin bypass · Response parity · Header parity · hreflang · canonical URL · HSTS · HSTS preload list · Content-Security-Policy · CSP nonce · edge cache · cache split · cache-buster · Cache-Control · Age header · render-blocking resource · payload text share · lazy loading · 404 and 410 status codes
Questions about CDN
What is CDN?
A distributed network that serves content near clients and absorbs traffic from the origin.
Which area of the glossary does CDN belong to?
HTTP, edge and rendering: The delivery layer between an origin and a client: proxies, caches, redirects, status codes and the headers that decide what a crawler actually received.
← Reverse proxy · Edge node →
See it in the full glossary · 731 terms across 19 areas.