Introduction

• CORS is the most common nightmare for developers
• Browsers by default prevent cross-domain requests
• This can restrict communication between your application and various other applications, and servers on the internet
• In this post, we’ll dive deeper into CORS
• We’ll understand what it is, how it works, why developers face the CORS problem, and how to get around it with examples
• In the end, we will also explore how you can solve CORS Issues on your device

What is CORS?

• CORS is a mechanism that allows resources to be requested from a different domain than the one from which it originated
• Diagram showing CORS
• It’s a security feature implemented by modern browsers that control access to resources from different origins
• CORS was introduced in 2004 by the World Wide Web Consortium (W3C) as a solution to the same-origin policy limitations.
• CORS is a critical concept for web developers, as it allows cross-domain communication and data sharing, which are essential in modern web applications.

Preflight Requests

• Preflight requests are HTTP OPTIONS requests sent by the browser to the server to determine if the cross-origin request is allowed.
• Preflight requests are necessary when a request does not meet the criteria for a Simple Request, such as using custom headers or HTTP methods other than GET and POST.