X-IInfo
Responses from Imperva-protected sites include the X-IInfo unofficial response header, an encoded metadata string carrying session, routing, and timing information for Imperva's internal diagnostics.
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, followed by a
four-character flag group (combinations of N, Y,
P, and C), then parenthesized groups labeled CT,
RT, q, and r. Some values end with a B segment
and a U segment. Imperva does not document any of the
field meanings. Community interpretation reads the
leading integers as node and session identifiers, the
RT group as a Unix timestamp with a duration in
milliseconds, and the remaining groups as connection
and routing metrics, but none of this is confirmed.
The entire string is an opaque correlation token. The individual fields are internal to Imperva and not intended for external consumption.
Example
A response from an Imperva-protected site shows the
typical structure. The leading integers
47-168755796-168755839 are read by community
interpretation as edge node and session identifiers,
and the first number in RT(1765318643229 196) lines
up with a Unix timestamp in milliseconds. The other
groups are opaque.
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 omits the CT group and carries a
B16 segment. The conditions producing each variant
are undocumented.
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 of additional undocumented values.
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.
