Theme App Extension: App Proxy strips Authorization header from request

Topic summary

A developer is experiencing an issue where the Authorization header is being stripped from fetch requests when routed through Shopify’s App Proxy in a theme app extension.

Key Details:

  • The app uses cookies for user authentication and makes fetch requests to display dynamic content on the storefront
  • This is a new behavior that started recently—everything worked correctly just days ago
  • Attached screenshots show request headers before and after passing through the App Proxy, clearly demonstrating the Authorization header’s removal

Current Status:

  • The developer checked Shopify’s App Proxy documentation and found no indication that Authorization is a disallowed header
  • Seeking confirmation if others are facing the same issue
  • No responses or resolution yet—the question remains open and unanswered
Summarized with AI on November 14. AI used: claude-sonnet-4-5-20250929.

Hey everyone,

I am building a Shopify app that has a theme app extension. From that theme app extension, I am doing some fetch requests to my server to display dynamic content to the customers using the app on the shop’s storefront. We may ask the user to authenticate themselves, and we do that by simply setting a cookie in the browser.

The issue is that whenever I do a fetch request that is handled by the App proxy, the Authorization header is stripped from the request. This is a new behavior that just started happening. Everything used to be working a couple of days ago.

The way I am doing my request is by simply doing a fetch request and adding an authorization header to it.

Below are attached screenshots of the request headers before and after they were handled by the App Proxy. We can clearly see in the second screenshot that the Authorization header isn’t there anymore. I checked the documentation of the app proxy and nowhere it says that Authorization is a disallowed header.

Is anyone facing the same issue? Any help would be much appreciated

Thank you

Before app proxy redirect

After app proxy redirect