---
title: ":authority pseudo-header is now properly forwarded to h2_backend apps"
description: "Apps using h2_backend now receive the original :authority pseudo-header from fly-proxy."
date: "2026-02-27"
author: "Pavel Borzenkov"
url: "https://fly.io/changelog/h2-backend-authority-header/"
discussion: "https://community.fly.io/t/authority-pseudo-header-is-now-properly-forwarded-to-h2-backend-apps/27236"
---

# :authority pseudo-header is now properly forwarded to h2_backend apps

HTTP/1 apps rely on the `Host` header to determine the original hostname a request was sent to.

Apps that enable the [`h2_backend`](https://fly.io/docs/reference/configuration/#http_service-http_options-h2_backend) option can’t really do this, as HTTP/2 simply doesn’t have a `Host` header. Instead, in the HTTP/2 world, the hostname is passed down in the `:authority` pseudo-header.

Previously, `fly-proxy` didn’t forward the original `:authority` pseudo-header, so when we added the `h2_backend` option, we just continued sending the `Host` header. However, not all languages and frameworks allow access to it for HTTP/2 requests. For example, Go still lets you access the `Host` header even if it differs from `:authority`, while ASP .NET replaces the `Host` header entirely with the value from `:authority`.

To make sure apps written in any language or framework can see the original hostname, `fly-proxy` now properly forwards the original request’s `:authority` to `h2_backend` apps.