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Cache Keys

A Cache Key is an identifier that Cloudflare uses for a file in our cache, and the Cache Key Template defines the identifier for a given HTTP request. For example, consider the following HTTP request on a TLS connection:

GET /logo.jpg HTTP/1.1
Host: www.cloudflare.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/77.0.3865.90 Safari/537.36
Accept: image/jpg

The default Cache Key constructed from this request combines aspects such as Cloudflare Zone ID, scheme, hostname, and path into a Cache Key similar to 1234:https://www.example.com/foo.jpg. Zone ID and Path are always included in the Cache Key and cannot be modified.

To create a Cache Key, see Create a Custom Cache Key.

Cache Key Template

There are a couple of common reasons to change the Cache Key Template. You might change the Cache Key Template to:

  • Fragment the cache so one URL is stored in multiple files. For example, to store different files based on a specific query string in the URL.
  • Consolidate the cache so different HTTP requests are stored in the same file. For example, to remove the Origin header added to Cloudflare Cache Keys by default.

For cross-origin requests, such as one from anotherdomain.com to example.com, the Origin HTTP request header results in a Cache Key with the ${header:origin} token populated as anotherdomain.com::https://www.example.com/something.

A Cache Level of Ignore Query String creates the following Cache Key: ${header:origin}::${scheme}://${host_header}${uri_iqs}

${uri_iqs} is replaced with the request path excluding the query string, so a request for http://example.com/file.jpg?something=123 creates the following Cache Key: ::http://example.com/file.jpg

Cache Key Settings

The following fields control the Cache Key Template.

Query String

The query string controls which URL query string parameters go into the Cache Key. You can include specific query string parameters or exclude them using the respective fields. When you include a query string parameter, the value of the query string parameter is used in the Cache Key.

Example

If you include the query string foo in a URL like https://www.example.com/?foo=bar, then bar appears in the Cache Key. Exactly one of include or exclude is expected.

Usage notes

  • To include all query string parameters (the default behavior), use include: "*"
  • To ignore query strings, use exclude: "*"
  • To include most query string parameters but exclude a few, use the exclude field which assumes the other query string parameters are included.

Headers

Headers control which headers go into the Cache Key. Similar to Query String, you can include specific headers or exclude default headers.

When you include a header, the header value is included in the Cache Key. For example, if an HTTP request contains an HTTP header like X-Auth-API-key: 12345, and you include the X-Auth-API-Key header in your Cache Key Template, then 12345 appears in the Cache Key.

To check for the presence of a header without including its actual value, use the check_presence option.

Currently, you can only exclude the Origin header. The Origin header is always included unless explicitly excluded. Including the Origin header in the Cache Key is important to enforce CORS. Additionally, you cannot include the following headers:

  • Headers that have high cardinality and risk sharding the cache
    • accept
    • accept-charset
    • accept-encoding
    • accept-datetime
    • accept-language
    • referer
    • user-agent
  • Headers that re-implement cache or proxy features
    • connection
    • content-length
    • cache-control
    • if-match
    • if-modified-since
    • if-none-match
    • if-unmodified-since
    • range
    • upgrade
  • Headers that are covered by other Cache Key features
    • cookie
    • host
  • Headers that are specific to Cloudflare and prefixed with cf-, e.g. cf-ray
  • Headers that are already included in the custom Cache Key template, e.g. origin

Host

Host determines which host header to include in the Cache Key.

  • If resolved: false, Cloudflare includes the Host header in the HTTP request sent to the origin.
  • If resolved: true, Cloudflare includes the Host header that was resolved to get the origin IP for the request. In this scenario, the Host header may be different from the header actually sent if the Cloudflare Resolve Override feature is used.

Like query_string or header, cookie controls which cookies appear in the Cache Key. You can either include the cookie value or check for the presence of a particular cookie.

Usage notes

You cannot include cookies specific to Cloudflare. Cloudflare cookies are prefixed with __cf, e.g. __cflb

User features

User feature fields add features about the end-user (client) into the Cache Key.

  • device_type classifies a request as mobile, desktop, or tablet based on the User Agent
  • geo includes the client’s country, derived from the IP address
  • lang includes the first language code contained in the Accept-Language header sent by the client