Fix CORS Errors in React & Express (Finally Explained) | Dev Series
Welcome to Video 4 of the Node.js & Express Series! We've built a full CRUD API in Express and a React frontend in the earlier series — today we finally connect them, and run straight into the #1 wall every beginner hits the first time: CORS.
📌 What you'll learn in this video:
Why a React app and an Express API are different "origins" even on localhost
What CORS actually is, and why the error only shows up in the browser
Fixing CORS properly with the cors npm package
Calling your own API from React with a custom hook + environment variables
Sending data with a real POST form, and why fetch() needs res.ok checked manually
Building a fully connected Quotes app: live GET + working POST, frontend to backend
⏱ TIMESTAMPS
0:00 — Intro
0:26 — Section 1: Recap — two apps, two ports
4:20 — Section 2: The CORS problem
6:43 — Section 3: Fixing CORS with the cors package
12:00 — Section 4: Calling your own API from React
20:00 — Outro & what's next
📝 Full written notes (GitHub, free):
https://github.com/lokesh1jha/Placeme...
⬅️ Previous Video (CRUD API + Postman — Video 3):
• You Can't Test This With Just a Browser (H...
➡️ Coming Next (Video 5 — Final Project: Full REST API with Express):
Coming Soon...
🎯 Interview topics covered in this video:
Same-origin policy and what counts as a different origin
What CORS is, and why Postman never shows CORS errors
Enabling and restricting CORS with the cors package
Environment variables for frontend API URLs (Vite's VITE_ prefix)
Why fetch() doesn't throw on 4xx/5xx responses
🔗 Full Web Dev Series playlist:
• Crack Placements Step-by-Step | No More Co...
💬 Got stuck anywhere? Drop your question in the comments — I reply to every one.
👍 If this helped, a like and subscribe genuinely helps the channel reach more freshers preparing for placements.
#CORS #React #Express #NodeJS #WebDevelopment #FullStackDevelopment #LearnToCode #TechIndia
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