CORS Proxy: Everything You Need to Know

by Reynaldi

January 3, 2025

CORS or “Cross-Origin Resource Sharing” is a mechanism for server to determine which origins can have access to a resource. While this security measure helps protect against unauthorized cross-origin requests, it can make fetching data from certain APIs challenging. That’s where a CORS proxy comes in. Below, we break down what a CORS proxy is, when you might need one, and how to use it.

What Is a CORS Proxy?

If you’ve developed a web app, you’ve likely encountered a CORS error at some point. CORS proxy is a service that helps you bypass CORS errors. They way it works is instead of fetching resources directly, only to run into CORS error, your request goes through the proxy first. The proxy handles the interaction with the target server, then returning the data to your app without triggering the error.

When to Use a CORS Proxy?

You’ll want to use a CORS proxy if:

The API or resource you’re trying to fetch doesn’t provide CORS headers.
You’re working on a frontend-only or static site without a backend.
You need a quick fix for “no ‘Access-Control-Allow-Origin’ header” errors.

However, if you have your own server, you could handle requests there, effectively doing what the proxy would do. But for frontend apps, a CORS proxy is an easy and quick solution.

How to Use a CORS Proxy?

Whenever you’re stuck with a CORS error while fetching external resources, simply prepend the proxy’s URL to your target endpoint. For example, if you’re using proxy.corsfix.com:

fetch("https://proxy.corsfix.com/?https://example.com/api")
  .then((response) => response.json())
  .then((data) => console.log(data))
  .catch((err) => console.error(err));

This reroutes your request through the proxy, which fetches data from the API on your behalf.

Conclusion

You can use CORS proxy whenever you need to fetch data from an API you don’t control to bypass the CORS errors. Hopefully, this gives you a clearer idea of how a CORS proxy works and why it’s so useful. The next time you face a pesky CORS error, you’ll know exactly what to do!