Why do browsers have 3 characters as protocol separator? [closed]

Question

http:// vs http:

Either there is some historical reason or I'm missing something.

Answer 1

According to RFC 1738,

While the syntax for the rest of the URL may vary depending on the particular scheme selected, URL schemes that involve the direct use of an IP-based protocol to a specified host on the Internet use a common syntax for the scheme-specific data:

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

Some or all of the parts "user:password@", ":password", ":port", and "/url-path" may be excluded. The scheme specific data start with a double slash "//" to indicate that it complies with the common Internet scheme syntax.