How to Fix CORS Error in Svelte

Reynaldi • September 7, 2025

If you’re running into a No Access-Control-Allow-Origin error in your Svelte project, you’re not alone. In this guide, you’ll learn how to instantly fix CORS errors, understand why they happen, and compare solutions so you can quickly get back to building your website.

CORS Error

Instant Fix (30 seconds)

Use Corsfix to instantly solve your CORS errors in Svelte. Simply add the proxy URL before your API calls, and you’ll be able to connect to the API without errors.

// instead of
fetch("https://api.example.com/data");

// use Corsfix
fetch("https://proxy.corsfix.com/?" + "https://api.example.com/data");

This solution works instantly in development environments (localhost) without any registration.

For live websites, set up your domain (takes 30 seconds), then your website can access the data without CORS errors.

Why do CORS errors happen?

Cross-Origin Resource Sharing errors happen because the target API you’re trying to call does not return the CORS headers. Without these headers, your browser won’t be able to access that API’s data.

Access-Control-Allow-Origin: https://website.com

The Access-Control-Allow-Origin header

This header controls whether a website can access the API. Although not all APIs have this, which is why the error happens in the first place.

Comparing Solutions

Using Corsfix (Best)

With Corsfix, you can solve your CORS issues instantly by simply adding our proxy URL before your target API. Our server will relay your request and return it to you with the appropriate CORS headers, solving the errors.

<script>
  import { onMount } from 'svelte';
  let data;
  onMount(async () => {
    data = await fetch('https://proxy.corsfix.com/?' + 'https://api.example.com/data').then((x) => x.json());
  });
</script>

<pre>
  {JSON.stringify(data, null, 2)}
</pre>

Code example for fixing CORS error in Svelte

Setting up your own backend

It’s possible to set up your own backend to fix CORS errors. However, since there are so many different backend frameworks and technologies, we can’t cover them all in one article, but the general idea is you would:

1. Create a new backend server (Node.js, Python, PHP, etc.)
2. Set up a relay endpoint that receives requests from your Svelte app
3. Forward the request to the target API on behalf of your frontend
4. Add the proper CORS headers to allow your Svelte app to access the response
5. Return the API response back to your Svelte application

This means you’re essentially building your own proxy server. You’ll need to handle error cases, manage different HTTP methods (GET, POST, PUT, DELETE), deal with authentication headers, ensure your server stays online 24/7, manage server hosting costs, SSL certificates, and ongoing maintenance.

Temporary Solutions

Some other solutions you might find when trying to fix CORS errors are:

• Installing a CORS unblock browser extension
• Disabling browser security features
• Using a local proxy

However, these workarounds are temporary solutions that only work on your own machine. When your website visitors try to access your site, they’ll still encounter CORS errors because these fixes don’t work for end users.

Conclusion

Use Corsfix to instantly solve CORS errors in Svelte. Understanding how CORS works is essential when working with third-party APIs, knowing your options help you choose the right solution.

Corsfix is free to get started, and you only need to upgrade when you go to production.