Solved: cors header missing vue api gateway

Often, when developing APIs using Vue and the AWS API Gateway, you encounter a ubiquitous issue: a missing CORS header. This can be confusing and stressful, especially when your application fully relies on the API for its function. Comprehensively, this obstacle is crucial to overcome for seamless API integration.

CORS, or Cross-Origin Resource Sharing, is a mechanism that uses additional HTTP headers to permit a browser to access resources from an origin (domain, protocol, or port) other than its own. In other words, it allows a web application at one domain to access resources from another domain. This feature is vital in restricting requests that might compromise security.

// Example code indicating a CORS issue
const app = express();
app.get('/no-cors', (req, res) => {
    text: 'You should not see this via a CORS request.'

Solution to “CORS header missing” issue

The solution to this problem is relatively simple: explicitly enable CORS in your Vue application and API Gateway settings. Specifically, you need to tweak a few settings in your Vue project and the AWS API gateway.

// Example of enabling CORS in Vue
const app = express();
const cors = require('cors');

Step-by-step explanation of the code

Let’s break down the code step by step:

  • The first step is to import the express library, which is a Node.js web application framework.
  • Next, the cors library is imported. This Node.js package provides an Express/Connect middleware to enable CORS with various options.
  • Finally, the app.use(cors()) function call uses the cors middleware for all paths and HTTP verbs (GET, POST, etc.). This enables CORS for the entire application.

Dealing with CORS headers in AWS API Gateway

After solving the issue in your Vue application, it’s time to address AWS. AWS API Gateway has headers explicitly designed to accept CORS requests. To enable them:

  • Navigate to the AWS API Gateway console.
  • Choose the API that’s giving you trouble.
  • Select the ‘Actions’ dropdown menu, then choose ‘Enable CORS’.
  • Finally, deploy your API once again to reflect these changes.

In conclusion, while daunting at first, the ‘CORS header missing’ issue is an easily solvable problem when developing APIs using Vue and AWS API Gateway. It requires an understanding of Express middleware, notably CORS, and knowledge of AWS settings. As always in development, remember to test your application thoroughly after implementing these fixes to ensure other areas weren’t adversely affected. With that, you should be well on your way to making the most of Vue API integrations.

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