X-CDN
The HTTP X-CDN unofficial response header identifies which CDN or WAF provider served the response, most commonly set by Imperva and other edge network services.
Usage
The X-CDN header is set by CDN or WAF providers to signal their presence in the delivery chain. Unlike the Server header, which identifies the origin software, X-CDN names the edge network or security service sitting in front of the origin.
The header appears most frequently on responses from Imperva (formerly Incapsula) and its related services. Other CDN providers sometimes set the same header with their own name, making X-CDN a loose convention rather than a standardized field. The value is informational and carries no Caching or routing semantics.
Values
CDN provider name
The most common value is a CDN or WAF brand name.
Imperva is the dominant value in the wild, reflecting
sites protected by Imperva Cloud WAF. Other observed
values include Served-By-Zenedge (Zenedge, acquired
by Oracle), Akamai, and fastly.
Generic cache label
Some implementations set the value to a generic label
rather than a brand, such as staticcache observed on
Shopee properties, confirming caching involvement
without naming the provider. This form is less common
and provides no identifying detail.
Example
A response from a site protected by Imperva Cloud WAF includes the provider name directly.
X-CDN: Imperva
A site served through Fastly sets the header to its lowercase brand name. The value format varies by provider since no specification governs the field.
X-CDN: fastly
Zenedge-based configurations use a descriptive string instead of a plain brand name.
X-CDN: Served-By-Zenedge
When the header carries a generic label, the CDN confirms its presence without disclosing the provider name. Identifying the specific CDN requires checking other headers like Server or Powered-By.
X-CDN: staticcache