X-Redirect
During phased deployments on Microsoft's own web properties, the X-Redirect unofficial response header carries a deployment-phase label, appearing on ordinary responses as well as redirects.
Usage
The X-Redirect header surfaces internal deployment
metadata. The single observed deployment is Microsoft's
azure.microsoft.com site, where the header carries the
opaque string Production-Phase3 on both
3xx redirect responses and
plain 200 responses.
Phased deployment models shift traffic gradually
between rings or stages, and a value such as
Production-Phase3 reads as the third phase of a
production rollout. On a redirect it accompanies the
Location header naming the destination;
on an ordinary response it simply tags the serving
stage. The label lets operators confirm
which configuration stage served a response without
inspecting infrastructure dashboards.
The header is not part of any HTTP specification. Its format and values are defined entirely by the serving infrastructure and carry meaning only within the deployment context.
Values
Values are opaque strings defined by the serving infrastructure. No standardized set of values exists. Observed formats include:
Production-Phase3: the only observed value, a named deployment phase on Microsoft's own infrastructure
Example
A Microsoft-hosted redirect carries the deployment-phase label alongside the Location header naming the destination.
HTTP/1.1 301 Moved Permanently
Location: https://azure.microsoft.com/en-us
X-Redirect: Production-Phase3
The same label appears on ordinary responses that issue no redirect.
HTTP/1.1 200 OK
Content-Type: text/html
X-Redirect: Production-Phase3