CORS Error Kya Hai? 2 Min Mein Fix (Express, FastAPI, Vite) | Hindi

"blocked by CORS policy: No 'Access-Control-Allow-Origin' header" — ye error har developer ko kabhi na kabhi aata hai

Is video mein simple Hinglish mein:
CORS kya hai: browser ka security guard
Origin = protocol + domain + port
Postman mein kyun chalta hai, browser mein kyun nahi
Preflight (OPTIONS) request kya hoti hai
Fix: Node Express (cors package), Python FastAPI (CORSMiddleware), Vite proxy
3 galtiyan: credentials + *, origin mein trailing slash, no-cors jugaad

auraautomation.site

Is video mein: CORS error kya hota hai, Postman me API chalti hai par browser me kyun block hoti hai, aur Express, FastAPI ya Vite proxy se ise 2 minute me kaise fix kare.
इस वीडियो में: कॉर्स एरर क्या है, ब्राउज़र रिक्वेस्ट क्यों ब्लॉक करता है और सर्वर पर इसे कैसे ठीक करें।
In this video: What a CORS error is, why the browser blocks the response, and how to fix it on the server with Express, FastAPI or a Vite proxy.