Can X-FORWARDED-FOR contain multiple IPs

Question

Can X-FORWARDED-FOR contain multiple IP addresses? If so, why? An illustrative example would be great.

Answer 1

Yes, if a request is chained through more than one proxy server, then each proxy should add the IP of the preceding one to the existing X-Forwarded-For header so that the entire chain is preserved.

Answer 2

From https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-For

X-Forwarded-For: <client>, <proxy1>, <proxy2>

If a request goes through multiple proxies, the IP addresses of each successive proxy is listed. This means, the right-most IP address is the IP address of the most recent proxy and the left-most IP address is the IP address of the originating client.

Examples:

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, 70.41.3.18, 150.172.238.178