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CDN-Cache-Control

CDN-Cache-Control is a response header field set on the origin to separately control the behavior of CDN caches from other intermediaries that might handle a response. You can set the CDN-Cache-Control or Cloudflare-CDN-Cache-Control response header using the same directives used with the Cache-Control .

Header precedence

You have several options available to determine how CDN-Cache-Control directives interact with Cache-Control directives.

An origin can:

  • Return the CDN-Cache-Control response header which Cloudflare evaluates to make caching decisions. Cache-Control, if also returned by the origin, is proxied as is and does not affect caching decisions made by Cloudflare. Additionally, CDN-Cache-Control is proxied downstream in case there are other CDNs between Cloudflare and the browser.

  • Return the Cloudflare-CDN-Cache-Control response header. This results in the same behavior as the origin returning CDN-Cache-Control except Cloudflare does not proxy Cloudflare-CDN-Cache-Control downstream because it’s a header only used to control Cloudflare. This option is beneficial if you want only Cloudflare to have a different caching behavior while all other downstream servers rely on Cache-Control or if you do not want Cloudflare to proxy the CDN-Cache-Control header downstream.

  • Return both Cloudflare-CDN-Cache-Control and CDN-Cache-Control response headers. In this case, Cloudflare only looks at Cloudflare-CDN-Cache-Control when making caching decisions because it is the most specific version of CDN-Cache-Control and proxies CDN-Cache-Control downstream. Only forwarding CDN-Cache-Control in this situation is beneficial if you want Cloudflare to have a different caching behavior than other CDNs downstream.

Interaction with other Cloudflare features

Edge Cache TTL page rule

The Edge Cache TTL page rule overrides the amount of time an asset is cached on the edge (Cloudflare data centers). This page rule overrides directives in Cloudflare-CDN-Cache-Control/CDN-Cache-Control which manage how long an asset is cached on the edge. You can set this page rule from the rules section of the dashboard.

Browser Cache TTL page rule

The Browser Cache TTL page rule overrides the amount of time an asset is cached by browsers/servers downstream of Cloudflare. Browser Cache TTL only modifies the Cache-Control response header. This page rule does not modify Cloudflare-CDN-Cache-Control/CDN-Cache-Control response headers.

Other Origin Response Headers

The origin returns the Expires response header which specifies the amount of time before an object is considered stale to the browser. This response header does not affect the caching decision at Cloudflare when Cloudflare-CDN-Cache-Control/CDN-Cache-Control is in use.

Cloudflare Default cache values

In situations where Cloudflare does not receive Cloudflare-CDN-Cache-Control, CDN-Cache-Control, or Cache-Control values, cacheable assets use the general default values.

When to use CDN-Cache-Control

Manage cached assets TTLs

Use CDN-Cache-Control when you want to manage cached asset’s TTLs separately for origin caches, CDN caches, and browser caches. Previously, this scenario required creating page rules, but CDN-Cache-Control accomplishes the desired behavior through origin-set response headers. The example below shows how you could manage your cached asset’s TTLs.

Headers:

  • Cache-Control: max-age=14400, s-maxage=84000
  • Cloudflare-CDN-Cache-Control: max-age=24400
  • CDN-Cache-Control: 18000

Cache behavior:

CachesCache TTL (seconds)
Origin Server Cache14400
Network Shared Cache84000
Cloudflare Edge24400
Other CDNs18000
Browser Cache14400

Specify when to serve stale content

Use CDN-Cache-Control headers in conjunction with Cache-Control headers to specify when to serve stale content in the case of error or during revalidation. The example below shows how you might set your headers and directives to apply to CDNs when handling errors.

Headers:

  • Cache-Control: stale-if-error=400
  • Cloudflare-CDN-Cache-Control: stale-if-error=60
  • CDN-Cache-Control: stale-if-error=200

Behavior in response to 5XX error:

CachesStale served (seconds) in response to error
Origin Cache Layer/Network Cache/Browser Cache400 (if it assumes the directive applies)
Cloudflare Edge60
Other CDN200