Failed to load response data: No data found for resource with given identifier

Matthew C.

—August 15, 2024

The Problem

When using browser dev tools, like Chrome DevTools, to investigate why a fetch request has failed, you may see the following error in the Network tab on the browser dev tools response panel:

Failed to load response data: No data found for resource with given identifier

This can be caused by cross-origin resource sharing (CORS), if your frontend code and the API endpoint are served from different origins and you haven’t set up CORS correctly.

It can also be caused by an incorrect request URL or a connection issue with the server.

The Solution

If the issue is caused by cross-origin resource sharing (CORS), you’ll see the following error in your browser dev tools Console tab:

Access to fetch at 'http://localhost:1338/api/sync' from origin 'http://localhost:5173' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

The CORS header ‘Access-Control-Allow-Origin’ missing error indicates that you need to set up CORS on your server to allow your frontend to access your backend API resources. Add your frontend origin (URL) to the Access-Control-Allow-Origin header. In an Express app, you can install the CORS npm package and add an origin, as shown in the code below:

import express from "express";
import cors from "cors";

const corsOptions = {
  origin: "http://localhost:5173"
};

const app = express();
app.use(cors(corsOptions));

You can use an API development platform, such as Insomnia or Postman, to test whether the fetch request has a CORS issue. The same-origin policy is a browser security measure that restricts resource fetching from different origins. Insomnia and Postman don’t enforce CORS. To learn more, take a look at this Sentry answer: Why does my JavaScript code receive a “No Access-Control-Allow-Origin header is present on the requested resource” error, while Postman does not?.

If CORS isn’t the issue, make sure that your API route exists.

If the request URL is incorrect, or if there is a server connection issue, you’ll see a “Not Found” error in your browser dev tools Console tab:

POST http://localhost:1338/api/syncc net::ERR_FAILED 404 (Not Found)

Note

You may only see the Failed to load response data: No data found for resource with given identifier error after multiple page reloads or page navigations if you’re using the Network tab in the dev tools of a Chromium browser and have the preserve log feature enabled. There is a Chromium issue about why some requests that initially show a response later show the error, after further page refreshes or navigation: DevTools: XHR (and other resources) content not available after navigation.