What are the headers added by ALB?

Question

Hi there,

Can you tell me, which headers an ALB adds to requests? (e.g. X-Forwarded-Proto?)
I could only find the [list for Classic Load Balancing](https://docs.aws.amazon.com/elasticloadbalancing/latest/classic/x-forwarded-headers.html) with no reference to ALB itself.

Customer example explained:
My customer has problems with mixed content requests (Tomcat server on EC2 doesn't know, that the client reached via HTTPS and SSL got terminated on ALB). Therefore we need to configure listening on headers, but we have no information about "What an ALB is delivering" so far.

Accepted Answer

See the [http headers section][1] of the ELB documentation. Excerpt:

> Application Load Balancers and Classic Load Balancers add X-Forwarded-For, X-Forwarded-Proto, and X-Forwarded-Port headers to the request.

> For front-end connections that use HTTP/2, the header names are in lowercase. Before the request is sent to the target using HTTP/1.1, the following header names are converted to mixed case: X-Forwarded-For, X-Forwarded-Proto, X-Forwarded-Port, Host, X-Amzn-Trace-Id, Upgrade, and Connection. All other header names are in lowercase.

[1]: https://docs.aws.amazon.com/elasticloadbalancing/latest/userguide/how-elastic-load-balancing-works.html

What are the headers added by ALB?

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