Cf-Ray
Every request passing through the Cloudflare network receives a unique identifier. The Cf-Ray response header is an unofficial, Cloudflare-specific header carrying this identifier for request tracing and debugging.
Usage
The Cf-Ray header is added by Cloudflare to every HTTP response passing through its network. The value is an opaque request identifier ending in a code naming the data center handling the request. Servers behind Cloudflare also receive this header as a request header, making end-to-end request tracing possible.
Adding the Cf-Ray value to origin server logs
helps match proxied requests to entries in
server-side logs. In NGINX, the value is accessible
through the $http_cf_ray variable. Full request
data, including ingress data center details, is
available through Cloudflare Logs, with current
access requirements in the Cloudflare dashboard.
Directives
ray-id
The ray-id is a hashed value uniquely
identifying the request. While each request
receives a ray ID, uniqueness is not strictly
guaranteed across all requests.
datacenter-code
The datacenter-code is a three-letter IATA
airport code identifying the Cloudflare data center
processing the request. For example, LAX
represents the Los Angeles data center and SJC
represents San Jose.
The visitor-facing response header names the ingress data center. The request header the origin receives is generated closer to the origin connection, so the two codes differ on routed paths such as Argo Smart Routing or Tiered Cache.
Example
The value is split into two parts separated by a
hyphen. The first part is the ray ID, a unique hash
for the request. The second part is an IATA airport
code identifying the Cloudflare data center. In
this case, SJC refers to the San Jose, California
data center.
Cf-Ray: 9ab9830f8f01234f-SJC
The same website requested from a different
geographic location routes through a different data
center. Here EWR refers to the Newark, New Jersey
data center.
Cf-Ray: 9b7d22ba0cdcde9c-EWR
When troubleshooting, the ray ID is the value to provide to Cloudflare support or to search for in log files. The data center code helps confirm which edge location handled the request.