A content delivery network (CDN) is a group of servers that delivers web content from locations closer to visitors. A CDN can cache eligible files at its edge, so repeated requests may be served without going back to the origin server. Many CDNs also act as reverse proxies and offer routing or security services.
What a CDN Changes for a Crawler
A crawl request may reach a CDN edge first. The response can be a cached copy, a fresh response from the origin, or a challenge or error generated at the edge. The response headers can help explain what happened: cache status and Age may indicate whether a stored copy was served, while a vendor-specific header can identify a challenge.
This matters when checking freshness or comparing pages from different regions. A successful request does not always mean the origin was contacted, and an edge cache can serve a version that has not yet been revalidated. Record the response time, headers, and location context when those details affect the collection.
CDN Does Not Mean Every Page Is Cached
Static assets such as images, CSS, and JavaScript are often cacheable. Dynamic HTML may be bypassed unless the site owner configures caching rules. The origin’s cache headers, CDN rules, cookies, and query strings can all affect behavior. Avoid assuming every response from a CDN is stale—or that every page is cached.
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