Why do browsers have 3 characters as protocol separator?

Question

http: // vs http:

Either there is some historical reason, or something is missing.

Answer 1

According to RFC 1738 ,

Although the syntax of the rest of the URL may vary depending on the particular scheme chosen, URL schemes that include direct use of the IP protocol for a specified host on the Internet use a common syntax for data specific to the scheme:

// user: password @ host: port / url path

Some or all of the parts "user: password @", ": password", ": port" and "/ url-path" may be excluded. A particular data schema begins with a double slash "//" to indicate that it matches the general syntax of the Internet schema.

Answer 2

// Indicates that contact with the server should be reached. (For example, when sending email, the notation 'mailto:<email address>...' can be used, without a slash). Please note that this does not mean a connection between the browser and the server. When the browser sent the request, there is no connection between the browser and the server.