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HTTP Header
X-Forwarded-For
NetworkingCarries the original client IP address when requests pass through proxies or load balancers.
HTTP header reference, syntax, examples, and developer usage.
What is the X-Forwarded-For header?
The X-Forwarded-For HTTP header is used to transmit metadata between a client and server as part of HTTP requests or responses.
HTTP headers define how content should be interpreted, cached, authenticated, secured, or processed by browsers and APIs.
Direction
This header may appear in both HTTP requests and responses.
Syntax
X-Forwarded-For: client, proxy1, proxy2
Example
X-Forwarded-For: 203.0.113.1
Common use cases
- Reverse proxy setups
- Client IP logging
- Rate limiting and analytics
Common mistakes
- Using the header in the wrong request or response context
- Sending invalid header values
- Incorrect header syntax
- Assuming the header automatically changes server behaviour