X-IInfo
The HTTP X-IInfo response header is an unofficial HTTP header containing encoded request metadata from Imperva's cloud WAF and CDN platform.
Usage
The X-IInfo header is added by Imperva (formerly Incapsula) to every response passing through its edge network. The value is an opaque string encoding session, request, and routing information used by Imperva's internal systems for diagnostics and request tracing.
The primary use case is support ticket correlation. When troubleshooting delivery or security issues on an Imperva-protected site, providing the X-IInfo value to Imperva support allows their team to locate the exact request in internal logs. The value also helps Imperva engineers identify which edge node handled the request, the connection state, and timing data.
Clients and origin servers have no reason to parse the value. The encoded fields are not documented publicly and the format changes across Imperva infrastructure versions.
Note
The "X-" naming convention for HTTP headers, "X" referring to "experimental", has been deprecated and needs to be transitioned to the formal naming convention for HTTP headers.
Values
Encoded metadata string
The value is a dash-and-space-separated string of
numeric and alphanumeric tokens. A typical value starts
with a set of dash-separated integers encoding a node
identifier, session counter, and sequence number. This
is followed by a four-character connection state flag
(combinations of N, Y, P, and C), then
parenthesized groups labeled CT (connection timing),
RT (request timing), q (queue metrics), and r
(retry counters). Some values end with a B segment
(backend info) and a U segment (upstream indicator).
The entire string is an opaque correlation token. The individual fields are internal to Imperva and not intended for external consumption.
Example
A cached response from an Imperva-protected site
includes timing and connection data. The leading
integers 47-168755796-168755839 identify the edge
node and session. NNNN reflects the connection state
flags. CT(46 58 0) contains connection timing values
and RT(1765318643229 196) records a request timestamp
with processing duration in milliseconds.
X-IInfo: 47-168755796-168755839 NNNN CT(46 58 0)
RT(1765318643229 196) q(0 0 1 0) r(4 4) U24
A shorter value appears when the request was not served
from cache. The 0NNN connection state and absence of
a CT group indicate a direct pass-through. The B16
segment records backend routing details.
X-IInfo: 4-1737500-0 0NNN RT(1770838596353 608)
q(0 -1 -1 -1) r(0 -1) B16 U18
Some responses include a B11 segment with a
parenthesized tuple encoding backend pool information.
X-IInfo: 14-67820078-0 0NNN
RT(1770151366257 50) q(0 -1 -1 0) r(0 -1)
B11(11,3577749,0) U18
When contacting Imperva support, the full X-IInfo string is the value to provide alongside the X-CDN header for fastest ticket resolution.
Takeaway
The X-IInfo header is an Imperva-specific request metadata string attached to every response from the Imperva Cloud WAF. The value acts as a correlation token for support tickets and internal log tracing across Imperva's edge infrastructure.