What is an empty Referer in anti-leech settings?

What is the difference between setting anti-leech protection and not specifying a blank Referer?

What is a referer?

Here, the Referer refers to a field in the HTTP header, also known as the HTTP source address (HTTP Referer), used to indicate the link from where to the current webpage. The format is URL. In other words, the HTTP referer header web page can be used to check where visitors come from, which is often used to deal with forged cross-site requests.

The correct English spelling of Referer is referrer. Due to spelling errors in earlier HTTP specifications, errors will occur to maintain backward compatibility. The specification of other network technologies attempts to correct this issue and use correct spelling, so the current spelling is not uniform.

For example, if you click the URL next to the data source Wikipedia, the browser will generate an HTTP request sent to the Web server of Wikipedia, the request will contain a referer field (that is, the address of this page): http://kb.qiniu.com/52pw6cde

Source: http://zh.wikipedia.org/wiki/httpreference address

What is an empty Referer? When will blank Referer appear?

First, we define a blank Referer as that the content in the referer header is null, or an HTTP request does not contain a referer header.

When will the HTTP request not contain the Referer field? According to the Referer definition, the function of a referer is to indicate where a request is linked. When a request is not triggered by a link, naturally, you do not need to specify the link source of the request.

For example, if you directly enter a resource URL in the address bar of a browser, such a request will not contain the Referer field, because it is an HTTP request generated out of thin air, it is not linked from a place.

In anti-leech settings, what is the difference between allowing empty Referer and not allowing empty Referer?

In anti-leech whitelist settings, if the White List contains an empty Referer, you can directly access the resource URL in the address bar of a browser;

However, if a blank Referer is not required, direct access via a browser is also forbidden.

What is an empty Referer in anti-leech settings?