Origin server

An origin server is the system that holds or generates the original website content before a delivery service such as a content delivery network (CDN) sends it to visitors. The origin may be a single server, a group of servers, or a hosting platform; the term describes its role as the source behind an intermediary.

When does a CDN contact the origin?

If a CDN has a usable temporarily stored copy, it can serve that copy without contacting the origin for that request. If the content is missing, expired, or configured not to be cached, the CDN asks the origin for a response and may pass the result back to the visitor. For example, a shop's product image might be served from a nearby cache, while a current shopping-cart request is sent to the origin application.

Is the origin server the same as the public server address?

Not necessarily. A domain's public DNS records may point to a CDN, a proxy that handles requests on the site's behalf, or a load balancer that shares requests across servers. That visible address can receive the visitor's request and then contact the origin privately. The origin might therefore have a different address and may not be directly reachable by ordinary visitors.

If the origin is unavailable, a CDN may continue serving some cached content but cannot fetch uncached content. The effect depends on cache freshness and service settings.

Related terms

• Content delivery network — may cache content in front of the origin
• Hosting provider — may operate the servers and network systems at the origin
• IP address — can identify a destination on a network
• DNS — directs requests to a public-facing service