What are CORS headers and why are they important?

What are CORS headers and why are they important?

CORS stands for Cross-Origin Resource Sharing. It's a security feature that allows or restricts resources on a web page to be requested from another domain outside the domain from which the first resource was served.

How do CORS headers work in practice?

CORS headers work by sending specific HTTP headers that tell the browser whether to allow or deny requests from different origins. For example, the 'Access-Control-Allow-Origin' header specifies which domains are permitted to access the resource.

What happens if CORS headers are not set correctly?

If CORS headers are not set correctly, browsers will block requests from different origins, leading to errors like 'No Access-Control-Allow-Origin header is present on the requested resource'.

Can you give me an example of how to set CORS headers in a server response?

Sure! In a Node.js Express server, you can set CORS headers like this:

app.use((req, res, next) => {
  res.header('Access-Control-Allow-Origin', '*'); // Allow all origins
  next();
});