HTTP: The Definitive Guide

A Sea of Schemes

In this section, we’ll take a look at the more common scheme formats on the Web. Appendix A gives a fairly exhaustive list of schemes and references to their individual documentation.

Table 2-4 summarizes some of the most popular schemes. Reviewing Section 2.2 will make the syntax portion of the table a little more familiar.

Table 2-4. Common scheme formats

Scheme	Description
http	The Hypertext Transfer Protocol scheme conforms to the general URL format, except that there is no username or password. The port defaults to 80 if omitted. Basic form: http://<host>:<port>/<path>?<query>#<frag> Examples: http://www.joes-hardware.com/index.html http://www.joes-hardware.com:80/index.html
https	The https scheme is a twin to the http scheme. The only difference is that the https scheme uses Netscape’s Secure Sockets Layer (SSL), which provides end-to-end encryption of HTTP connections. Its syntax is identical to that of HTTP, with a default port of 443. Basic form: https://<host>:<port>/<path>?<query>#<frag> Example: https://www.joes-hardware.com/secure.html
mailto	Mailto URLs refer to email addresses. Because email behaves differently from other schemes (it does not refer to objects that can be accessed directly), the format of a mailto URL differs from that of the standard URL. The syntax for Internet email addresses is documented in Internet RFC 822. Basic form: mailto:<RFC-822-addr-spec> Example: mailto:[e-mail]
ftp	File Transfer ...