HTTP 401 Unauthorized

HTTP status code 401, also known as "Unauthorized," is a crucial response status in web development and API communications.

It indicates that the client's request has not been fulfilled because it lacks valid authentication credentials.

A typical scenario involving a 401 status code is when accessing a protected endpoint in a REST API. The client needs to include a valid token or API key in the request headers. If this authentication token is expired, invalid, or absent, the server will deny access, returning a 401 response.

It's important to note that a 401 status code is different from a 403 status code, which means "Forbidden." While 401 indicates a lack of proper authentication, 403 signifies that the server understood the request but refuses to authorize it, even if valid credentials are provided.

In summary, HTTP status code 401 serves as a security measure, ensuring that only authenticated clients can access certain resources, thereby protecting sensitive data and functionalities.