463 X-Forwarded-For Too Long

AWS load balancer code for a request whose X-Forwarded-For header contains more than 30 addresses.

Status

HTTP/1.1 463 X-Forwarded-For Too Long

Details

Category: 4xx
Status: Unofficial (AWS Elastic Load Balancing). Not registered with IANA. A server, framework, or CDN convention.
Specification: none, not defined by any RFC
Cacheable: Not cacheable
Response body: Allowed
Retry: Retry only after changing the request

An AWS Application Load Balancer rejects a request with 463 when the X-Forwarded-For header lists more than 30 IP addresses. A chain that long normally means a proxy loop or a header being appended repeatedly.

The fix is almost always upstream: find the hop that keeps adding to the header rather than raising a limit.

Common causes

A proxy loop appending an address on every pass.
A long chain of nested proxies or CDNs, each adding a hop.
A client sending a spoofed X-Forwarded-For with many entries.

How to fix it

As the client

Do not send your own X-Forwarded-For. Let the infrastructure populate it.
Flatten the proxy chain so a request passes through fewer hops.

As the server

Strip or normalize inbound X-Forwarded-For at the edge instead of appending blindly.
Look for routing loops where traffic re-enters the same load balancer.

Examples

GET /api/status HTTP/1.1
Host: api.example.com
X-Forwarded-For: (31 addresses)

HTTP/1.1 463