X-Forwarded-For (XFF) header is a de-facto standard header for identifying the originating IP address of a client connecting to a web server through an HTTP proxy or a load balancer. When traffic is intercepted between clients and servers, server access logs contain the IP address of the proxy or load balancer only. To see the original IP address of the client, the
X-Forwarded-For request header is used.
This header is used for debugging, statistics, and generating location-dependent content and by design it exposes privacy sensitive information, such as the IP address of the client. Therefore the user's privacy must be kept in mind when deploying this header.
A standardized version of this header is the HTTP
X-Forwarded-For is also an email-header indicating that an email-message was forwarded from another account.
X-Forwarded-For: <client>, <proxy1>, <proxy2>
X-Forwarded-For: 2001:db8:85a3:8d3:1319:8a2e:370:7348 X-Forwarded-For: 203.0.113.195 X-Forwarded-For: 203.0.113.195, 126.96.36.199, 188.8.131.52
Other non-standard forms:
# Used for some Google services X-ProxyUser-Ip: 203.0.113.19
Not part of any current specification. The standardized version of this header is
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