Development
February 1, 2024
5 min read

Fixing CORS Issues in APIs the Right Way

CORS errors are common in web APIs. This guide shows how to fix them securely and permanently.

MD AL AMIN CHOWDHURY

Software Engineer

540
Fixing CORS Issues in APIs the Right Way

Fixing CORS Issues in APIs


Cross-Origin Resource Sharing (CORS) protects browsers from malicious requests, but it often breaks development flows.


Common Error


`Access to fetch at 'http://api.domain.com' from origin 'http://localhost:3000' has been blocked by CORS policy.`


Solution (Node.js/Express)


const cors = require('cors');
app.use(cors({ origin: 'http://localhost:3000' }));

Tips


  • Never use `'*'` in production.
  • Use dynamic origin whitelist if needed.
  • Set proper headers: `Access-Control-Allow-Origin`, `Methods`, `Headers`.

    • Conclusion


    Proper CORS handling ensures both security and developer productivity.


    Tags

    #CORS#API#Security#Express

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