The URL is composed of several parts. The http: in the URL specifies a URL method, which is to be used for retrieving the document or performing the action. There are several alternatives.

The following URL methods may be found. Note that some of these are implementation dependant:

• http: - Hypertext Transfer Protocol. See RFC 2068

• https: - Secure Hypertext Transfer Protocol.

• ftp: - File Transfer Protocol. See RFC 1738

• news: - USENET news. See RFC 1738

• snews: - Secure USENET news.

• mailto: - Electronic mail address. See RFC 2368

• telnet: - Reference to interactive sessions. See RFC 1738

• file: - Host-specific file names. See RFC 1738

These are special Netscape URL request methods that invoke internal sub-systems. Some of these may not be fully functional or may need to be activated by configuration options in the prefs.js file:

• nethelp: - Help manager.

• about: - Internal browser resources.

• mailbox: - Mailbox manager.

• view-source: - Source viewer.

• javascript: - JavaScript interpreter.

• livescript: - JavaScript interpreter.

• mocha: - JavaScript interpreter.

• imap: - internet message access protocol. See RFC 2192

• pop3: - Post Office Protocol v3. See RFC 2384

• ldap: - Local Directory Access Protocol.

• ldaps: - Local Directory Access Protocol (secure).

• rlogin: - Remote login.

• tn3270: - Interactive 3270 emulation sessions.

• wais: - Wide Area Information Servers. See RFC 1738

• wysiwyg: - JavaScript generated page content.

The MSIE browser also uses the clsid: URL to locate registered ActiveX controls that are loaded with the <OBJECT> tag.

The IANA documention also lists these protocols:

• gopher: - The Gopher Protocol. See RFC 1738

• nntp: - USENET news using NNTP access. See RFC 1738

• prospero: - Prospero Directory Service. See RFC 1738

• z39.50s: - Z39.50 Session. See RFC 2056

• z39.50r: - Z39.50 Retrieval. See RFC 2056

• cid: - content identifier. See RFC 2392

• mid: - message identifier. See RFC 2392

• vemmi: - versatile multimedia interface. See RFC 2122

• service: - service location. See RFC 2609

• nfs: - network file system protocol. See RFC 2224

• acap: - application configuration access protocol. See RFC 2244

• rtsp: - real time streaming protocol. See RFC 2326

• tip: - Transaction Internet Protocol. See RFC 2371

• data: - data. See RFC 2397

• dav: - dav. See RFC 2518

• opaquelocktoken: - opaquelocktoken. See RFC 2518

• sip: - session initiation protocol. See RFC 2543

• tel: - telephone. See RFC 2806

• fax: - fax. See RFC 2806

• modem: - modem. See RFC 2806

• afs: - Andrew File System global file names.

• mailserver: - Access to data available from mail servers

These are specified as part of the ATVEF standard to provide support for TV set top boxes:

• tv: - Display a TV picture where you might use an image.

• lid: - Local identifier for accessing cached and carousel delivered assets.

• uhttp: - Unidirectional (broadcast) HTTP content.

Warnings:

• As of autumn 2000, there are changes afoot to allow characters other than the English letters and numbers to be used in URL values. The Verisign organisation will act as an arbiter of whether a URL is valid but it may be composed of arabic and Chinese characters for example.