Checkout "Not Found" Error on Headless Shopify App – Checkout URL Format Issue

Shopify Discussion
1

Hello, I am reaching out for help because my Shopify headless app’s checkout flow has suddenly stopped working.

Issue Summary
Whenever I try to redirect customers to the checkout using the URL returned from Shopify’s API, I receive a “Not Found” error page on the checkout site.

This problem began on July 23, 2025, after 9:51 PM IST. Before that, everything was working.

The issue only affects checkouts created from our headless app. The same flow works on our main website storefront.

Checkout URL Details
The checkout URL we receive from Shopify API looks like this:

text

or, after swapping the domain to our custom domain:

text

  1. Has Shopify recently changed how checkout URLs are generated or accepted for headless apps?

–Should the checkout URL include any segment (such as cart ID) before /checkouts/?

–Is there a new required format for checkout URLs for headless or API-generated checkouts?

  1. Is anyone else seeing checkout URLs returned from the Storefront API with an extra segment (like a cart ID) in the path?

–If so, what is the correct way to handle or transform this URL?

  1. How should we safely convert the API-returned URL to our custom domain and ensure it works?

–Is it valid to simply replace the .myshopify.com domain with our custom domain as per Shopify best practices?

–Or is there a setting to ensure API returns the correct domain in the checkout URL for headless integrations?

  1. Are there any recent Shopify platform updates that may have broken headless app checkouts created via API?

–Any notice of required changes for stores using custom domains and headless setups?

  1. What is the recommended Shopify-supported approach to reliably obtain a valid checkout URL from the API for redirection?