In the HTTP protocol, there are different statuses for showing how requests are processed by servers. One of these statuses is "HTTP 306 (Unused)." It's worth noting that this status is actually one of those HTTP statuses that is no longer used and has been very limitedly utilized in previous HTTP versions. Please allow for more explanation.
Essentially, HTTP 306 (Unused) was designed to indicate that a user's request has temporarily been redirected to another URL; meaning that a proxy exists during the request. However, due to the reasons that are not clearly specified, this HTTP status code has never been used in practice, and it is no longer mentioned as part of the HTTP standard.
This means that if you encounter the HTTP 306 status code, you should not handle it because it certainly does not mean "this code has been masked". Many modern servers do not produce this status code because its usefulness has been diminished.
Incidents related to this code have never been implemented in real scenarios, and this is why it has not been explicitly mentioned in more recent documentation. Generally, HTTP status codes like 307 (Temporary Redirect) or 308 (Permanent Redirect) are recommended and are utilized for handling different redirects.
Therefore, it can be said that status 306 is more of an artifact from a historical standpoint in the realm of HTTP statuses. Understanding it does not help to solve any practical problem, but occasionally it may assist in better understanding the historical context and the evolution of standards.
Continuing, let's look at the structure of a command that may have been used for this purpose. However, we must reiterate that there is no need for practical use of this code:
HTTP/1.1 306 Unused
Location: http://www.example.com/redirect_here/
Please let’s examine this line by line:
HTTP/1.1 306 Unused
The HTTP request returns with status 306 indicating that it has not been used.
Location: http://www.example.com/redirect_here/
This line indicates where the request should be redirected; although in practice, it is never redirected.