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URI scheme

URI scheme

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Encyclopedia
In the field of computer networking, a URI scheme is the top level of the Uniform Resource Identifier
Uniform Resource Identifier
In computing, a uniform resource identifier is a string of characters used to identify a name or a resource on the Internet. Such identification enables interaction with representations of the resource over a network using specific protocols...

 (URI) naming structure. All URIs and absolute URI references are formed with a scheme name, followed by a colon character
Colon (punctuation)
The colon is a punctuation mark consisting of two equally sized dots centered on the same vertical line.-Usage:A colon informs the reader that what follows the mark proves, explains, or lists elements of what preceded the mark....

 (":"), and the remainder of the URI called (in the outdated RFCs
Request for Comments
In computer network engineering, a Request for Comments is a memorandum published by the Internet Engineering Task Force describing methods, behaviors, research, or innovations applicable to the working of the Internet and Internet-connected systems.Through the Internet Society, engineers and...

 1738 and 2396, but not the current STD 66/RFC 3986) the scheme-specific part. The syntax and semantics of the scheme-specific part are left largely to the specifications governing individual schemes, subject to certain constraints such as reserved characters and how to "escape
Escape character
In computing and telecommunication, an escape character is a character which invokes an alternative interpretation on subsequent characters in a character sequence. An escape character is a particular case of metacharacters...

" them.

URI schemes are frequently erroneously referred to as "protocols", or specifically as URI protocols or URL protocols, since most were originally designed to be used with a particular protocol, and often have the same name. The http scheme, for instance, is generally used for interacting with Web resources
Resource (Web)
The concept of resource is primitive in the Web architecture, and is used in the definition of its fundamental elements. The term was first introduced to refer to targets of Uniform Resource Locators , but its definition has been further extended to include the referent of any Uniform Resource...

 using HyperText Transfer Protocol
Hypertext Transfer Protocol
The Hypertext Transfer Protocol is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web....

. Today, URIs with that scheme are also used for other purposes, such as RDF
Resource Description Framework
The Resource Description Framework is a family of World Wide Web Consortium specifications originally designed as a metadata data model...

 resource identifiers and XML namespaces, that are not related to the protocol. Furthermore, some URI schemes are not associated with any specific protocol (e.g. "file
File URI scheme
The file URI scheme is a URI scheme specified in RFC 1630 and RFC 1738, typically used to retrieve files from within one's own computer.- Format :A file URL takes the form of file://host/path...

") and many others do not use the name of a protocol as their prefix (e.g. "news").

URI schemes should be registered with IANA
Internet Assigned Numbers Authority
The Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System , media types, and other Internet Protocol-related symbols and numbers...

, although non-registered schemes are used in practice. RFC 4395 describes the procedures for registering new URI schemes.

Generic syntax


Internet standard
Internet standard
In computer network engineering, an Internet Standard is a normative specification of a technology or methodology applicable to the Internet. Internet Standards are created and published by the Internet Engineering Task Force .-Overview:...

 STD 66 (also RFC 3986) defines the generic syntax to be used in all URI schemes. Every URI is defined as consisting of four parts, as follows:

: [ ? ] [ # ]

The scheme name consist of a sequence of characters beginning with a letter and followed by any combination of letters, digits, plus ("+"), period ("."), or hyphen ("-"). Although schemes are case-insensitive, the canonical form is lowercase and documents that specify schemes must do so with lowercase letters. It is followed by a colon (":").

The hierarchical part of the URI is intended to hold identification information hierarchical in nature. Usually this part begins with a double forward slash ("//"), followed by an authority part and an optional path.
  • The authority part holds an optional user information part terminated with "@" (e.g. username:password@), a hostname (i.e. domain name
    Domain name
    A domain name is an identification string that defines a realm of administrative autonomy, authority, or control in the Internet. Domain names are formed by the rules and procedures of the Domain Name System ....

     or IP address
    IP address
    An Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...

    ), and an optional port number
    TCP and UDP port
    In computer networking, a port is an application-specific or process-specific software construct serving as a communications endpoint in a computer's host operating system. A port is associated with an IP address of the host, as well as the type of protocol used for communication...

     preceded by a colon ":".

  • The path part is a sequence of segments (conceptually similar to directories
    Directory (file systems)
    In computing, a folder, directory, catalog, or drawer, is a virtual container originally derived from an earlier Object-oriented programming concept by the same name within a digital file system, in which groups of computer files and other folders can be kept and organized.A typical file system may...

    , though not necessarily representing them) separated by a forward slash ("/"). Each segment can contain parameters separated from it using a semicolon (";"), though this is rarely used in practice.


The query
Query string
In World Wide Web, a query string is the part of a Uniform Resource Locator that contains data to be passed to web applications such as CGI programs....

is an optional part separated with a question mark, which contains additional identification information which is not hierarchical in nature. The query string
Query string
In World Wide Web, a query string is the part of a Uniform Resource Locator that contains data to be passed to web applications such as CGI programs....

 syntax is not generically defined, but is commonly organized as a sequence of = pairs separated by a semicolon or separated by an ampersand, for example:
Semicolon: key1=value1;key2=value2;key3=value3
Ampersand: key1=value1&key2=value2&key3=value3

The fragment
Fragment identifier
In computer hypertext, a fragment identifier is a short string of characters that refers to a resource that is subordinate to another, primary resource...

is an optional part separated from the front parts by a hash
Number sign
Number sign is a name for the symbol #, which is used for a variety of purposes including, in some countries, the designation of a number...

 ("#"). It holds additional identifying information that provides direction to a secondary resource, e.g. a section heading in an article identified by the remainder of the URI. When the primary resource is an HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....

 document, the fragment is often an id attribute of a specific element and web browser
Web browser
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...

s will make sure this element is visible.

Examples


The following are two example URIs and their component parts (taken loosely from RFC 3986 — STD 66):

foo://username:password@example.com:8042/over/there/index.dtb?type=animal&name=narwhal#nose
\_/ \_______________/ \_________/ \__/ \___/ \_/ \______________________/ \__/
| | | | | | | |
| userinfo hostname port | | query fragment
| \________________________________/\_____________|____|/
| | | | |
scheme name authority path | |
| | |
| path interpretable as filename
| ___________|____________ |
/ \ / \ |
urn:example:animal:ferret:nose interpretable as extension

Official IANA-registered schemes


The official URI schemes registered with the IANA
Internet Assigned Numbers Authority
The Internet Assigned Numbers Authority is the entity that oversees global IP address allocation, autonomous system number allocation, root zone management in the Domain Name System , media types, and other Internet Protocol-related symbols and numbers...

 are as follows (note that "IETF Draft" in no way is a finalized specification and must not be treated so; refer to Section 2.2 of RFC 2026 for more details):
Scheme Purpose Defined by General format Notes
aaa Diameter Protocol RFC 3588 aaa://[:][;transport=][;protocol=]
example:

aaa://host.example.com:1813;transport=udp;protocol=radius
aaas Secure equivalent of aaa RFC 3588 aaas://[:][;transport=][;protocol=]
acap Application Configuration Access Protocol
Application Configuration Access Protocol
The Application Configuration Access Protocol is a protocol for storing and synchronizing general configuration and preference data. It was originally developed so that IMAP clients can easily access address books, user options, and other data on a central server and be kept in synch across all...

RFC 2244 acap://[[;AUTH=]@][:]/ URL scheme used within the ACAP protocol for the "subdataset" attribute, referrals and inheritance
cap Calendar access protocol RFC 4324 generic syntax URL scheme used to designate both calendar stores and calendars accessible using the CAP protocol
cid Referencing individual parts of an SMTP/MIME
MIME
Multipurpose Internet Mail Extensions is an Internet standard that extends the format of email to support:* Text in character sets other than ASCII* Non-text attachments* Message bodies with multiple parts...

 message
RFC 2111
RFC 2392
cid: e.g. referencing an attached image within a formatted e-mail. (See also mid:)
crid TV-Anytime
TV-Anytime
TV-Anytime is a set of specifications for the controlled delivery of multimedia content to a user's digital video recorder . It seeks to exploit the evolution in convenient, high capacity storage of digital information to provide consumers with a highly personalized TV experience...

 Content Reference Identifier
RFC 4078 crid:/// Allow references to scheduled publications of broadcast media content.
data Inclusion of small data items inline RFC 2397 data:[;base64],
dav HTTP Extensions for Distributed Authoring (WebDAV
WebDAV
Web-based Distributed Authoring and Versioning is a set of methods based on the Hypertext Transfer Protocol that facilitates collaboration between users in editing and managing documents and files stored on World Wide Web servers...

)
RFC 2518
RFC 4918
dav: Used for internal identifiers only; WebDAV itself addresses resources using the http: and https: schemes. http://article.gmane.org/gmane.org.w3c.uri/808
dict Dictionary service protocol
DICT
DICT is a dictionary network protocol created by the DICT Development Group. It is described by RFC 2229. Its goal is to surpass the Webster protocol and to allow clients to access more dictionaries during use...

RFC 2229 dict://;@:/d:::

dict://;@:/m::::
refer to definitions or word lists available using the DICT protocol
dns Domain Name System
Domain name system
The Domain Name System is a hierarchical distributed naming system for computers, services, or any resource connected to the Internet or a private network. It associates various information with domain names assigned to each of the participating entities...

RFC 4501 dns:[//[:]/][?]
examples:

dns:example?TYPE=A;CLASS=IN

dns://192.168.1.1/ftp.example.org?type=A
designates a DNS resource record set, referenced by domain name, class, type, and, optionally, the authority
fax Used for telefacsimile
Fax
Fax , sometimes called telecopying, is the telephonic transmission of scanned printed material , normally to a telephone number connected to a printer or other output device...

 numbers
RFC 2806
RFC 3966
fax: Deprecated in RFC 3966 in favour of tel:. Listed as "historical"
file
File URI scheme
The file URI scheme is a URI scheme specified in RFC 1630 and RFC 1738, typically used to retrieve files from within one's own computer.- Format :A file URL takes the form of file://host/path...

Addressing files on local or network file system
File system
A file system is a means to organize data expected to be retained after a program terminates by providing procedures to store, retrieve and update data, as well as manage the available space on the device which contain it. A file system organizes data in an efficient manner and is tuned to the...

s
RFC 1738
RFC 3986
file://[host]/path or

(RFC 3986) file:[//host]/path
Since this usually used for local files the host from RFC 1738 is often empty leading to a starting triple /. RFC 3986 allows an absolute path with no host part.
ftp FTP
File Transfer Protocol
File Transfer Protocol is a standard network protocol used to transfer files from one host to another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture and utilizes separate control and data connections between the client and server...

 resources
RFC 1738
IETF Draft
Old IETF Draft
generic syntax
geo
Geo URI
A geo' URI is a URI scheme defined by the Internet Engineering Task Force's RFC 5870 as:a Uniform Resource Identifier for geographic locations using the 'geo' scheme name...

A Uniform Resource Identifier for Geographic Locations RFC 5870 geo:,[,][;u=]
(for WGS-84
World Geodetic System
The World Geodetic System is a standard for use in cartography, geodesy, and navigation. It comprises a standard coordinate frame for the Earth, a standard spheroidal reference surface for raw altitude data, and a gravitational equipotential surface that defines the nominal sea level.The latest...

)
Other coordinate reference systems (including those for non-terrestrial globes, such as The Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 and Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

) will be supported, once registered.
go Common Name Resolution Protocol RFC 3368 go://[]?[]*[;=[,]] or
go:*[;=[,]]
gopher Used with Gopher protocol RFC 4266 gopher://:/
h323 Used with H.323
H.323
H.323 is a recommendation from the ITU Telecommunication Standardization Sector that defines the protocols to provide audio-visual communication sessions on any packet network...

 multimedia communications
RFC 3508 h323:[@][:][;]
http HTTP
Hypertext Transfer Protocol
The Hypertext Transfer Protocol is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web....

 resources
RFC 1738
RFC 2616
(makes
RFC 2068
obsolete)
generic syntax
https
Https
Hypertext Transfer Protocol Secure is a combination of the Hypertext Transfer Protocol with SSL/TLS protocol to provide encrypted communication and secure identification of a network web server...

HTTP connections secured using SSL/TLS
Transport Layer Security
Transport Layer Security and its predecessor, Secure Sockets Layer , are cryptographic protocols that provide communication security over the Internet...

RFC 2817 generic syntax
iax Inter-Asterisk eXchange protocol version 2 RFC 5456 iax:[@][:][/[?]]
examples:
iax:[2001:db8::1]:4569/alice?friends
iax:johnQ@example.com/12022561414
icap Internet Content Adaptation Protocol
Internet Content Adaptation Protocol
The Internet Content Adaptation Protocol is a lightweight HTTP-like protocol specified in RFC 3507 which is used to extend transparent proxy servers, thereby freeing up resources and standardizing the way in which new features are implemented. ICAP is generally used to implement virus scanning,...

RFC 3507
im Instant messaging
Instant messaging
Instant Messaging is a form of real-time direct text-based chatting communication in push mode between two or more people using personal computers or other devices, along with shared clients. The user's text is conveyed over a network, such as the Internet...

 protocol
RFC 3860 im:@ Works as xmpp: URI for single user chat sessions.
imap Accessing e-mail resources through IMAP RFC 2192
RFC 5092
imap://[[;AUTH=]@][:]/
info
Info:
In computer science, info: is a Uniform Resource Identifier scheme for information assets with identifiers in public namespaces that allows legacy namespaces such as Library of Congress Identifiers and Digital object identifiers to be represented as URIs...

Information Assets with Identifiers in Public Namespaces RFC 4452
ipp Internet Printing Protocol
Internet Printing Protocol
In computing, the Internet Printing Protocol provides a standard network protocol for remote printing as well as for managing print jobs, media size, resolution, and so forth....

RFC 3510
iris
iris.beep
iris.xpc
iris.xpcs
iris.lws
Internet Registry Information Service RFC 3981 RFC 3983 RFC 4992 RFC 4992 RFC 4993
ldap LDAP
Lightweight Directory Access Protocol
The Lightweight Directory Access Protocol is an application protocol for accessing and maintaining distributed directory information services over an Internet Protocol network...

 directory request
RFC 2255
RFC 4516
ldap://[[:]][/ [?[][?[][?[][?]]]]]
example:

ldap://ldap1.example.net:6666/o=University%20of%20Michigan, c=US??sub?(cn=Babs%20Jensen)
lsid Life Science Identifier
LSID
Life Science Identifiers are a way to name and locate pieces of information on the web. Essentially, an LSID is a unique identifier for some data, and the LSID protocol specifies a standard way to locate the data...

dtc/04-10-08 URN:LSID:::[:]
example:

urn:lsid:ubio.org:namebank:11815
mailto
Mailto
The mailto URI scheme, as registered with the Internet Assigned Numbers Authority , defines the scheme for Simple Mail Transfer Protocol email addresses...

SMTP
Simple Mail Transfer Protocol
Simple Mail Transfer Protocol is an Internet standard for electronic mail transmission across Internet Protocol networks. SMTP was first defined by RFC 821 , and last updated by RFC 5321 which includes the extended SMTP additions, and is the protocol in widespread use today...

 e-mail
E-mail
Electronic mail, commonly known as email or e-mail, is a method of exchanging digital messages from an author to one or more recipients. Modern email operates across the Internet or other computer networks. Some early email systems required that the author and the recipient both be online at the...

 addresses and default content
RFC 1738
RFC 2368
RFC 6068
mailto:
[?=[&=]]
example:

mailto:jsmith@example.com?subject=A%20Test&body=My%20idea%20is%3A%20%0A
Headers are optional, but often include subject=; body= can be used to pre-fill the body of the message.
mid Referencing SMTP/MIME
MIME
Multipurpose Internet Mail Extensions is an Internet standard that extends the format of email to support:* Text in character sets other than ASCII* Non-text attachments* Message bodies with multiple parts...

 messages, or parts of messages.
RFC 2111
RFC 2392
mid:[/] (See also cid:)
modem modem RFC 2806
RFC 3966
Deprecated in RFC 3966 in favour of tel:. Listed as "historical"
msrp
msrps
Message Session Relay Protocol
Message Session Relay Protocol
In computer networking, the Message Session Relay Protocol is a protocol for transmitting a series of related instant messages in the context of a communications session. An application instantiates the session with the Session Initiation Protocol or other rendez-vous methods.The MSRP protocol is...

RFC 4975
mtqp Message Tracking Query Protocol RFC 3887
mupdate Mailbox Update Protocol RFC 3656
news (Usenet
Usenet
Usenet is a worldwide distributed Internet discussion system. It developed from the general purpose UUCP architecture of the same name.Duke University graduate students Tom Truscott and Jim Ellis conceived the idea in 1979 and it was established in 1980...

) newsgroups and postings
RFC 1738
RFC 5538
news: or
news:
References a particular resource, regardless of location.
nfs Network File System resources RFC 2224 generic syntax
nntp Usenet NNTP
Network News Transfer Protocol
The Network News Transfer Protocol is an Internet application protocol used for transporting Usenet news articles between news servers and for reading and posting articles by end user client applications...

RFC 1738
RFC 5538
nntp://:// Referencing a specific host is often less useful than referencing the resource generically, as NNTP servers are not always publicly accessible
opaquelocktoken opaquelocktoken RFC 2518
RFC 4918
pop Accessing mailbox through POP3 RFC 2384 pop://[[;AUTH=]@][:]
pres Used in Common Profile for Presence (CPP) to identify presence RFC 3859 pres:
[?=[&=]]
Similar to "mailto:"
prospero Prospero Directory Service RFC 1738
RFC 4157
Listed as "Historical" by IANA.
rsync rsync
Rsync
rsync is a software application and network protocol for Unix-like and Windows systems which synchronizes files and directories from one location to another while minimizing data transfer using delta encoding when appropriate. An important feature of rsync not found in most similar...

RFC 5781 rsync://[:]/
rtsp Real Time Streaming Protocol
Real Time Streaming Protocol
The Real Time Streaming Protocol is a network control protocol designed for use in entertainment and communications systems to control streaming media servers. The protocol is used for establishing and controlling media sessions between end points...

RFC 2326
service RFC 2609
shttp Secure HTTP
Secure hypertext transfer protocol
Secure Hypertext Transfer Protocol is a little-used alternative to the HTTPS URI scheme for encrypting web communications carried over HTTP. S-HTTP is defined in RFC 2660. It was developed by Eric Rescorla and Allan M. Schiffman....

RFC 2660 Largely superseded by HTTPS
Https
Hypertext Transfer Protocol Secure is a combination of the Hypertext Transfer Protocol with SSL/TLS protocol to provide encrypted communication and secure identification of a network web server...

.
sieve ManageSieve protocol RFC 5804
sip Used with Session Initiation Protocol
Session Initiation Protocol
The Session Initiation Protocol is an IETF-defined signaling protocol widely used for controlling communication sessions such as voice and video calls over Internet Protocol . The protocol can be used for creating, modifying and terminating two-party or multiparty sessions...

 (SIP)
RFC 2543
RFC 3969
RFC 3261
sip:[:]@[:][;][?]
examples:

sip:alice@atlanta.com?subject=project%20x&priority=urgent

sip:+1-212-555-1212:1234@gateway.com;user=phone
sips Secure equivalent of sip RFC 3969
RFC 3261
sips:[:]@[:][;][?]
sms Interact with SMS
SMS
SMS is a form of text messaging communication on phones and mobile phones. The terms SMS or sms may also refer to:- Computer hardware :...

 capable devices for composing and sending messages.
RFC 5724 sms:?
examples:

sms:+15105550101?body=hello%20there

sms:+15105550101,+15105550102?body=hello%20there
Should be used as a subset to the tel: schema.
snmp Simple Network Management Protocol
Simple Network Management Protocol
Simple Network Management Protocol is an "Internet-standard protocol for managing devices on IP networks. Devices that typically support SNMP include routers, switches, servers, workstations, printers, modem racks, and more." It is used mostly in network management systems to monitor...

RFC 4088 snmp://[user@]host[:port][/[[;]][/]]
examples:

snmp://example.com//1.3.6.1.2.1.1.3+

snmp://tester5@example.com:8161/bridge1;800002b804616263
soap.beep
soap.beeps
RFC 3288
RFC 4227
tag Tag URI
Tag URI
Tag URI is a universal unique identifier protocol commonly used in various internet-related technologies and associated with data storage and transfer systems such as YAML....

RFC 4151 tag:,: Represented entities do not necessarily have to be accessible electronically.
tel Used for telephone numbers RFC 5341
RFC 3966
RFC 2806
tel:
telnet Used with telnet
TELNET
Telnet is a network protocol used on the Internet or local area networks to provide a bidirectional interactive text-oriented communications facility using a virtual terminal connection...

RFC 1738
RFC 4248
telnet://:@[:/]
tftp Trivial File Transfer Protocol
Trivial File Transfer Protocol
Trivial File Transfer Protocol is a file transfer protocol known for its simplicity. It is generally used forautomated transfer of configuration or boot files between machines in a local environment....

RFC 3617
thismessage multipart/related relative reference resolution RFC 2557
tip Transaction Internet Protocol RFC 2371
tv TV Broadcasts RFC 2838
urn Uniform Resource Name
Uniform Resource Name
A uniform resource name is a uniform resource identifier that uses the urn scheme and does not imply availability of the identified resource. Both URNs and URLs are URIs, and a particular URI may be a name and a locator at the same time.The functional requirements for uniform resource names are...

s
RFC 2141 urn::
vemmi Versatile Multimedia Interface RFC 2122
wais Used with Wide area information server
Wide area information server
Wide Area Information Servers or WAIS is a client–server text searching system that uses the ANSI Standard Z39.50 Information Retrieval Service Definition and Protocol Specifications for Library Applications" to search index databases on remote computers...

 (WAIS)
RFC 1738
RFC 4156
wais://:/[?] or wais://:/// Listed as "Historical" by IANA.
xmlrpc.beep
xmlrpc.beeps
RFC 3529
xmpp XMPP
Extensible Messaging and Presence Protocol
Extensible Messaging and Presence Protocol is an open-standard communications protocol for message-oriented middleware based on XML . The protocol was originally named Jabber, and was developed by the Jabber open-source community in 1999 for near-real-time, extensible instant messaging , presence...

RFC 4622
RFC 5122
xmpp:@[:]/[][?]
z39.50r Z39.50
Z39.50
Z39.50 is a client–server protocol for searching and retrieving information from remote computer databases. It is covered by ANSI/NISO standard Z39.50, and ISO standard 23950. The standard's maintenance agency is the Library of Congress....

 retrieval
RFC 2056 z39.50r://[:]/?[;esn=][;rs=]
z39.50s Z39.50 session RFC 2056 z39.50s://[:]/[][?][;esn=][;rs=]
Scheme Purpose Defined by General format Notes

Unofficial but common URI schemes

Scheme Purpose Defined by General format Notes
about
About: URI scheme
about is an internal URI scheme in various web browsers to display certain built-in functions...

Displaying product information and internal information IETF Draft See about URI scheme for more details. Widely used by web browser
Web browser
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...

s, sometimes even providing interactive resources. The Opera web browser
Opera (web browser)
Opera is a web browser and Internet suite developed by Opera Software with over 200 million users worldwide. The browser handles common Internet-related tasks such as displaying web sites, sending and receiving e-mail messages, managing contacts, chatting on IRC, downloading files via BitTorrent,...

 uses opera: instead.
adium
Adium
Adium is a free and open source instant messaging client for Mac OS X that supports multiple IM networks, including Windows Live Messenger, Yahoo! Messenger, Google Talk, AIM, ICQ, and XMPP. It supports many protocols through the libraries libezv , MGTwitterEngine , and libpurple...

xtra
Direct installation of Adium Xtras (plugins). The Adium Team adiumxtra://www.adiumxtras.com/download/0000 0000 refers to a specific Xtra
aim Controlling AOL Instant Messenger
AOL Instant Messenger
AOL Instant Messenger is an instant messaging and presence computer program which uses the proprietary OSCAR instant messaging protocol and the TOC protocol to allow registered users to communicate in real time. It was released by AOL in May 1997...

.
AOL
AOL
AOL Inc. is an American global Internet services and media company. AOL is headquartered at 770 Broadway in New York. Founded in 1983 as Control Video Corporation, it has franchised its services to companies in several nations around the world or set up international versions of its services...

aim:? Functions include goim, addbuddy, and buddyicon.
apt
Advanced Packaging Tool
The Advanced Packaging Tool, or APT, is a free user interface that works with core libraries to handle the installation and removal of software on the Debian GNU/Linux distribution and its variants...

Experimental method of installing software using APT
Advanced Packaging Tool
The Advanced Packaging Tool, or APT, is a free user interface that works with core libraries to handle the installation and removal of software on the Debian GNU/Linux distribution and its variants...

.
apt: Commonly found on websites which contain Debian software repositories.
afp Accessing Apple Filing Protocol
Apple Filing Protocol
The Apple Filing Protocol is a network protocol that offers file services for Mac OS X and original Mac OS. In Mac OS X, AFP is one of several file services supported including Server Message Block , Network File System , File Transfer Protocol , and WebDAV...

 shares
IETF Draft over TCP/IP: afp://[@][:][/[]]

over AppleTalk
AppleTalk
AppleTalk is a proprietary suite of protocols developed by Apple Inc. for networking computers. It was included in the original Macintosh released in 1984, but is now unsupported as of the release of Mac OS X v10.6 in 2009 in favor of TCP/IP networking...

:
afp:/at/[@][:][/]
aw
Active Worlds
Active Worlds is a 3D virtual reality platform. The Active Worlds client runs on Windows. Users assign themselves a name, log into the Active Worlds universe, and explore 3D virtual worlds and environments that other users have built. Users can chat with one another or build structures and areas...

Link to an Active Worlds world Activeworlds Inc. aw://:/ Mostly found in HTTP referers when users open a website from within a Active Worlds world.
bitcoin Send money to a Bitcoin
Bitcoin
Bitcoin is a decentralized, peer-to-peer network over which users make transactions that are tracked and verified through this network. The word Bitcoin also refers to the digital currency implemented as the currency medium for user transactions over this network...

 address
Bitcoin URI Scheme bitcoin:
[?[amount=][&][label=
bolo
Bolo (computer game)
Bolo is a video game created for the BBC Micro computer by Stuart Cheshire in 1987, and later ported to the Macintosh in its most popular incarnation. Most recently a Windows clone named Winbolo was developed by John Morrison. Cheshire's Bolo is a networked multiplayer game that simulates a tank...

Join an existing bolo game. bolo:/// Mostly passed via IRC or via tracker servers.
callto Launching Skype
Skype
Skype is a software application that allows users to make voice and video calls and chat over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system...

 call (+And in Hungary the KLIP Software call too) (unofficial; see also skype:)
Skype
Skype
Skype is a software application that allows users to make voice and video calls and chat over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system...

callto: or
callto: http://daringfireball.net/2005/12/callto_uris_safari
Introduced with Microsoft NetMeeting
Microsoft NetMeeting
Microsoft NetMeeting was a VoIP and multi-point videoconferencing client included in many versions of Microsoft Windows . It used the H.323 protocol for video and audio conferencing, and was interoperable with OpenH323-based clients such as Ekiga, and Internet Locator Service as reflector...

. Works with current version of Skype
Skype
Skype is a software application that allows users to make voice and video calls and chat over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system...

 with Firefox, Internet Explorer
Internet Explorer
Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...

 and Safari
Safari (web browser)
Safari is a web browser developed by Apple Inc. and included with the Mac OS X and iOS operating systems. First released as a public beta on January 7, 2003 on the company's Mac OS X operating system, it became Apple's default browser beginning with Mac OS X v10.3 "Panther". Safari is also the...

chrome Specifies user interfaces built using XUL in Mozilla-based browsers. Mozilla chrome:///
/ (Where
is either "content", "skin" or "locale")
Works only in Mozilla-based browsers such as Firefox, SeaMonkey and Netscape. Not related to the Google Chrome
Google Chrome
Google Chrome is a web browser developed by Google that uses the WebKit layout engine. It was first released as a beta version for Microsoft Windows on September 2, 2008, and the public stable release was on December 11, 2008. The name is derived from the graphical user interface frame, or...

 browser.
coap Accessing Constrained Application Protocol (CoAP) resources. IETF Draft coap://[:]/[?] Identify CoAP resources and provide a means of locating the resource.
content Accessing an Android content provider. Open Handset Alliance
Open Handset Alliance
The Open Handset Alliance is a consortium of 84 firms to develop open standards for mobile devices. Member firms include Google, HTC, Sony, Dell, Intel, Motorola, Qualcomm, Texas Instruments, Samsung Electronics, LG Electronics, T-Mobile, Nvidia, and Wind River Systems.-History:The OHA was...

content://provider/ Performs a query on an Android Content Provider
cvs Provides a link to a Concurrent Versions System
Concurrent Versions System
The Concurrent Versions System , also known as the Concurrent Versioning System, is a client-server free software revision control system in the field of software development. Version control system software keeps track of all work and all changes in a set of files, and allows several developers ...

 (CVS) Repository
Concurrent Versions System
Concurrent Versions System
The Concurrent Versions System , also known as the Concurrent Versioning System, is a client-server free software revision control system in the field of software development. Version control system software keeps track of all work and all changes in a set of files, and allows several developers ...

cvs://@/;[date=date to retrieve > tag=tag to retrieve]
doi
Digital object identifier
A digital object identifier is a character string used to uniquely identify an object such as an electronic document. Metadata about the object is stored in association with the DOI name and this metadata may include a location, such as a URL, where the object can be found...

Digital object identifier, a digital identifier for any object of intellectual property. IETF Draft doi:10./
Example: doi:10.1000/182
Used e.g. for most scientific publications.
Can be resolved via HTTP
Hypertext Transfer Protocol
The Hypertext Transfer Protocol is a networking protocol for distributed, collaborative, hypermedia information systems. HTTP is the foundation of data communication for the World Wide Web....

 (transormed into an URL
Uniform Resource Locator
In computing, a uniform resource locator or universal resource locator is a specific character string that constitutes a reference to an Internet resource....

) by prepending http://dx.doi.org/ or http://hdl.handle.net/ in front.
ed2k
Ed2k URI scheme
In computing, eD2k links are hyperlinks used to denote files stored on computers connected to the eDonkey filesharing P2P network.- General :...

Resources available using the eDonkey2000
EDonkey2000
eDonkey2000 was a peer-to-peer file sharing application developed by US company MetaMachine, using the Multisource File Transfer Protocol...

 network
eDonkey2000 ed2k://>file||||/ or
ed2k://|server|||/
Links to servers are also possible, as are additional parameters. Official documentation from
Facetime
FaceTime
FaceTime is a video calling software application and related protocol developed by Apple for supported mobile devices running the iOS, in addition to Macintosh computers running Mac OS X 10.6.6 and higher...

FaceTime is a video conferencing software developed by Apple for iPhone 4, the fourth generation iPod Touch, and computers running Mac OS X. Apple Inc. facetime://
>|
example:

facetime://+19995551234
Apple has not published documentation on this protocol yet.
feed web feed
Web feed
A web feed is a data format used for providing users with frequently updated content. Content distributors syndicate a web feed, thereby allowing users to subscribe to it. Making a collection of web feeds accessible in one spot is known as aggregation, which is performed by an aggregator...

 subscription
feed: or
feed://
examples:

feed://example.com/rss.xml

feed:https://example.com/rss.xml
See Feed URI scheme for a detailed overview of common implementations, supported software, and critics.
finger Querying user information using the Finger protocol
Finger protocol
In computer networking, the Name/Finger protocol and the Finger user information protocol are simple network protocols for the exchange of human-oriented status and user information.-Name/Finger protocol:...

IETF Draft finger://host[:port][/]
fish Accessing another computer's files using the SSH
Secure Shell
Secure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...

 protocol
fish KDE kioslave fish://[[:]@][:] See Files transferred over shell protocol for details about the protocol.
git Provides a link to a GIT repository Git
Git (software)
Git is a distributed revision control system with an emphasis on speed. Git was initially designed and developed by Linus Torvalds for Linux kernel development. Every Git working directory is a full-fledged repository with complete history and full revision tracking capabilities, not dependent on...

Github example: git://github.com/user/project-name.git
gg Starting chat with Gadu-Gadu
Gadu-Gadu
Gadu-Gadu is a Polish instant messaging client using a proprietary protocol. Gadu-Gadu is the most popular IM service in Poland, with over 15 million registered accounts and approximately 6.5 million users online daily. Gadu-Gadu’s casual gaming portal had some 500,000 active users at the end of...

 user
Gadu-Gadu
Gadu-Gadu
Gadu-Gadu is a Polish instant messaging client using a proprietary protocol. Gadu-Gadu is the most popular IM service in Poland, with over 15 million registered accounts and approximately 6.5 million users online daily. Gadu-Gadu’s casual gaming portal had some 500,000 active users at the end of...

gg:
gizmoproject Gizmo5
Gizmo5
Gizmo5 was a Voice over Internet Protocol communications network and a proprietary freeware soft phone for that network. On November 12, 2009, Google announced that it had acquired Gizmo5...

 calling link.
gizmoproject://call?id= May use sip:// instead of gizmoproject:// in recent versions of Gizmo5.
gtalk Start a chat with a Google Talk
Google Talk
Google Talk is a freeware voice over Internet protocol client application offered by Google Inc. The first beta version of the program was released on August 24, 2005...

 user
Google Talk
Google Talk
Google Talk is a freeware voice over Internet protocol client application offered by Google Inc. The first beta version of the program was released on August 24, 2005...

gtalk:chat?jid=example@gmail.com See Google Talk
Google Talk
Google Talk is a freeware voice over Internet protocol client application offered by Google Inc. The first beta version of the program was released on August 24, 2005...

, XMPP
Extensible Messaging and Presence Protocol
Extensible Messaging and Presence Protocol is an open-standard communications protocol for message-oriented middleware based on XML . The protocol was originally named Jabber, and was developed by the Jabber open-source community in 1999 for near-real-time, extensible instant messaging , presence...

, and http://juberti.blogspot.com/2006/11/gtalk-uri.html for more information
irc Connecting to an Internet Relay Chat
Internet Relay Chat
Internet Relay Chat is a protocol for real-time Internet text messaging or synchronous conferencing. It is mainly designed for group communication in discussion forums, called channels, but also allows one-to-one communication via private message as well as chat and data transfer, including file...

 server to join a channel.
IETF Draft
Old IETF Draft
irc://[:]/[[?]] Assuming the client knows a server associated with the name, "host" may optionally be an IRC network name.
ircs Secure equivalent of irc IETF Draft ircs://[:]/[[?]] See irc
irc6 IPv6
IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...

 equivalent of irc
irc6://[:]/[[?]] See irc
itms Used for connecting to the iTunes Music Store Apple Inc itms:
jar
JAR (file format)
In software, JAR is an archive file format typically used to aggregate many Java class files and associated metadata and resources into one file to distribute application software or libraries on the Java platform.JAR files are built on the ZIP file format and have the .jar file extension...

Compressed archive member Java API jar:!/[] Works for any ZIP
ZIP (file format)
Zip is a file format used for data compression and archiving. A zip file contains one or more files that have been compressed, to reduce file size, or stored as is...

 based file.
javascript Execute JavaScript
JavaScript
JavaScript is a prototype-based scripting language that is dynamic, weakly typed and has first-class functions. It is a multi-paradigm language, supporting object-oriented, imperative, and functional programming styles....

 code
IETF Draft javascript: Works in any modern browser.
keyparc Keyparc encrypt/decrypt resource. Bloombase keyparc://encrypt// or
keyparc://decrypt//
lastfm Connecting to a radio stream from Last.fm
Last.fm
Last.fm is a music website, founded in the United Kingdom in 2002. It has claimed 30 million active users in March 2009. On 30 May 2007, CBS Interactive acquired Last.fm for UK£140m ....

.
Last.fm
Last.fm
Last.fm is a music website, founded in the United Kingdom in 2002. It has claimed 30 million active users in March 2009. On 30 May 2007, CBS Interactive acquired Last.fm for UK£140m ....

lastfm:// or lastfm://globaltags/ or
lastfm://user//
ldaps Secure equivalent of ldap Old version of IETF Draft ldaps://[[:]][/ [?[][?[][?[][?]]]]] Not an IETF standard, but commonly used in applications.
magnet "magnet links" Magnet-URI Project magnet:?xt=urn:sha1:&dn=
(other parameters are also possible)
Used by various peer-to-peer
Peer-to-peer
Peer-to-peer computing or networking is a distributed application architecture that partitions tasks or workloads among peers. Peers are equally privileged, equipotent participants in the application...

 clients, usually providing the hash of a file to be located on the network.
maps "map links" maps:q= Some mobile web browsers will launch a dedicated mapping application. See also "geo:" (RFC 5870)
market Opens Android Market Android http://developer.android.com/guide/publishing/publishing.html
market://details?id=Package_name or
market://search?q=Search_Query or
market://search?q=pub:Publisher_Name
Supported by Android devices
message Direct link to specific email message Apple Inc http://daringfireball.net/2007/12/message_urls_leopard_mail message:
message://
Supported by Mail
Mail (application)
Mail is an email program included with Apple Inc.'s Mac OS X operating system. Originally developed by NeXT as NeXTMail, a part of their NeXTSTEP operating system, it was adapted, following Apple's acquisition of NeXT, to become OS X's Mail application.Mail uses the SMTP, POP3, and IMAP protocols,...

 since OS X 10.5
mms Windows streaming media mms://:/ Used by Windows Media Player to stream audio and/or video.
msnim Adding a contact, or starting a conversation in Windows Live Messenger Windows Live Messenger
Windows Live Messenger
Windows Live Messenger is an instant messaging client created by Microsoft that is currently designed to work with Windows XP , Windows Vista, Windows 7, Windows Mobile, Windows CE, Xbox 360, Blackberry OS, iOS, Java ME, S60 on Symbian OS 9.x and Zune HD...

Add a contact to the buddy list

msnim:add?contact=nada@example.com

Start a conversation with a contact

msnim:chat?contact=nada@example.com

Start a voice conversation with a contact

msnim:voice?contact=nada@example.com

Start a video conversation with a contact

msnim:video?contact=nada@example.com
Can be invoked from a web page or via a run command or an Internet Explorer browser URL (won't work with Firefox 2.0.0.8). For web pages use this HTML: Click to chat!
mumble Joining a server. Mumble mumble://[username[:password]@]
[:port]/[channelpath]?version=[&title=][&url=]
Official documentation from Mumble website
mvn Access Apache Maven
Apache Maven
Maven is a build automation and software comprehension tool. While primarily used for Java programming, it can also be used to build and manage projects written in C#, Ruby, Scala, and other languages. Maven serves a similar purpose to the Apache Ant tool, but it is based on different concepts and...

 repository artifacts
OPS4J mvn:org.ops4j.pax.web.bundles/service/0.2.0-SNAPSHOT
mvn:http://user:password@repository.ops4j.org/maven2!org.ops4j.pax.web.bundles/service/0.2.0
notes Open a Lotus Notes
Lotus Notes
Lotus Notes is the client of a collaborative platform originally created by Lotus Development Corp. in 1989. In 1995 Lotus was acquired by IBM and became known as the Lotus Development division of IBM and is now part of the IBM Software Group...

 document or database
Lotus Notes
Lotus Notes
Lotus Notes is the client of a collaborative platform originally created by Lotus Development Corp. in 1989. In 1995 Lotus was acquired by IBM and became known as the Lotus Development division of IBM and is now part of the IBM Software Group...

notes://
Used by IBM Lotus Notes to refer to documents and databases stored within the Lotus Notes system. When clicked in a browser on a computer with Lotus Notes client installed, Notes will open the document link as if a Notes DocLink were clicked within Notes.
palm Used to designate system services in HP webOS applications HP webOS palm:[/]]/ Official documentation from HP webOS Services Overview
paparazzi Used to launch and automatically take a screen shot using the application "Paparazzi!" (Mac
Mac OS
Mac OS is a series of graphical user interface-based operating systems developed by Apple Inc. for their Macintosh line of computer systems. The Macintosh user experience is credited with popularizing the graphical user interface...

 only)
Derailer paparazzi:[]http:[//[:[][]]/ Official documentation from the Paparazzi! website
psyc Used to identify or locate a person, group, place or a service and specify its ability to communicate PSYC psyc:[//[:[][]]/[][#] PSYC website>-
rmi Look up a Java object in an RMI registry. Sun
Sun Microsystems
Sun Microsystems, Inc. was a company that sold :computers, computer components, :computer software, and :information technology services. Sun was founded on February 24, 1982...

rmi://[:]/ URI scheme understood by JNDI. Can be used to lookup a remote Java object within an RMI registry (typically for the purposes of RMI
Java remote method invocation
The Java Remote Method Invocation Application Programming Interface , or Java RMI, is a Java application programming interface that performs the object-oriented equivalent of remote procedure calls ....

 on that object). Host/port in the URI are of the rmiregistry process, not the remote object.
rtmp Real Time Messaging Protocol
Real Time Messaging Protocol
Real Time Messaging Protocol was initially a proprietary protocol developed by Macromedia for streaming audio, video and data over the Internet, between a Flash player and a server...

Adobe Systems
Adobe Systems
Adobe Systems Incorporated is an American computer software company founded in 1982 and headquartered in San Jose, California, United States...

rtmp://// URI schema used to connect to Adobe Flash Media Server.
secondlife Open the Map floater in Second Life application to teleport the resident to the location. Linden Lab
Linden Lab
Linden Research, Inc., d/b/a Linden Lab, is a privately held American Internet company that is best known as the creator of Second Life....

secondlife:///// Used by SLurl.com. Knowledge base article.
sgn Social Graph Node Mapper Google
Google
Google Inc. is an American multinational public corporation invested in Internet search, cloud computing, and advertising technologies. Google hosts and develops a number of Internet-based services and products, and generates profit primarily from advertising through its AdWords program...

example:

sgn://social-network.example.com/?ident=bob
Official documentation from sgnodemapper project.
skype Launching Skype
Skype
Skype is a software application that allows users to make voice and video calls and chat over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system...

 call (unofficial; see also callto:)
Skype
Skype
Skype is a software application that allows users to make voice and video calls and chat over the Internet. Calls to other users within the Skype service are free, while calls to both traditional landline telephones and mobile phones can be made for a fee using a debit-based user account system...

skype:phonenumber>[?[add|call|chat|sendfile|userinfo]] Official documentation from Skype website.
spotify Load a track, album, artist, search, or playlist in Spotify Spotify
Spotify
Spotify is a Swedish-founded, UK-headquartered DRM-based music streaming service offering streaming of selected music from a range of major and independent record labels, including Sony, EMI, Warner Music Group, and Universal. Launched in October 2008 by Swedish startup Spotify AB, the service had...

spotify:album|track>: or
spotify:search: or
spotify:user::playlist:

example:
spotify:track:2jCnn1QPQ3E8ExtLe6INsx
Informally specified in Spotify official blog post by CTO Andreas Ehn.
ssh SSH
Secure Shell
Secure Shell is a network protocol for secure data communication, remote shell services or command execution and other secure network services between two networked computers that it connects via a secure channel over an insecure network: a server and a client...

 connections (like telnet:) and
IETF Draft ssh://[[;fingerprint=]@][:]
sftp SFTP
SSH file transfer protocol
In computing, the SSH File Transfer Protocol is a network protocol that provides file access, file transfer, and file management functionality over any reliable data stream...

 file transfers (not be to confused with FTPS
FTPS
FTPS is an extension to the commonly used File Transfer Protocol that adds support for the Transport Layer Security and the Secure Sockets Layer cryptographic protocols....

 (FTP/SSL))
IETF Draft sftp://[[;fingerprint=]@][:]//
smb Accessing SMB
Server Message Block
In computer networking, Server Message Block , also known as Common Internet File System operates as an application-layer network protocol mainly used to provide shared access to files, printers, serial ports, and miscellaneous communications between nodes on a network. It also provides an...

/CIFS shares
IETF Draft smb://[@][:][/[]][?=[;=]] or
smb://[@][:][/]
soldat Joining servers Soldat
Soldat
Soldat is a Polish 2D multiplayer game for Windows. It is a side-scroller inspired by Liero and Scorched Earth, combined with elements from Counter-Strike and Worms. The game is shareware...

soldat://:/[password]
example:

soldat://127.0.0.1:23073/thatssecret!
Official note in Manual
steam Interact with Steam: install apps, purchase games, run games, etc. Steam, Valve Corporation
Valve Corporation
Valve Corporation is an American video game development and digital distribution company based in Bellevue, Washington, United States...

steam: or
steam:///
Official documentation from Valve Developer Community website
svn Provides a link to a Subversion (SVN) source control repository Subversion svn[+ssh]://@<:port>/
teamspeak Joining a server. TeamSpeak
TeamSpeak
TeamSpeak is a proprietary Voice over IP software that allows users to speak on a chat channel with other users, much like a telephone conference call. A TeamSpeak user will often wear a headset with an integrated microphone...

teamspeak://[:]/[?=[&=]] Official documentation from TeamSpeak Website
things Send a to-do to Things. Cultured Code things:add?title=Buy%20milk¬es=Low%20fat&dueDate=2011-12-24 This URI scheme works on Mac OS & iOS, providing Things by Cultured Code is installed.
udp BitTorrent tracker protocol based on UDP. BitTorrent
UDP tracker
The UDP tracker protocol is a high-performance low-overhead BitTorrent tracker protocol. It uses the stateless User Datagram Protocol for data transmission instead of the HTTP protocol regular trackers use...

udp://[:]/ Documentation: UDP tracker protocol
unreal Joining servers Unreal
Unreal
Unreal is a first-person shooter video game developed by Epic MegaGames and Digital Extremes and published by GT Interactive in May 1998...

unreal://[:]/ Unreal legacy "protocol"
ut2004 Joining servers Unreal Tournament 2004
Unreal Tournament 2004
Unreal Tournament 2004, also known as UT2K4 and UT2004, is a futuristic first-person shooter computer game developed by Epic Games and Digital Extremes...

ut2004://[:][/?] Documentation from Unreal Developer Network
ventrilo Joining a server. Ventrilo
Ventrilo
Ventrilo is a proprietary VoIP software which includes text chat.The Ventrilo client and server are both available as freeware for use with fewer than 8 people on the same server . The server software is available for Microsoft Windows, Mac OS X, or Unix variants such as Linux, Kopi, Solaris,...

ventrilo://[:]/[?=[&=]] Official documentation from Ventrilo Website
view-source
View-source URI scheme
The view-source URI scheme is used by some browsers to construct URLs that refer to a source display for a given resource.For example, this URI would show the source of the page located at :view-source:http://www.example.com...

Shows a web page as code 'in the raw'. IANA registration template view-source:
where is specified in RFC 3986. Example:

view-source:http://en.wikipedia.org/wiki/URI_scheme
See view-source URI scheme
View-source URI scheme
The view-source URI scheme is used by some browsers to construct URLs that refer to a source display for a given resource.For example, this URI would show the source of the page located at :view-source:http://www.example.com...

 for details.
webcal Subscribing to calendars in iCalendar
ICalendar
iCalendar is a computer file format which allows Internet users to send meeting requests and tasks to other Internet users, via email, or sharing files with an extension of .ics...

 format
iCalendar
ICalendar
iCalendar is a computer file format which allows Internet users to send meeting requests and tasks to other Internet users, via email, or sharing files with an extension of .ics...

webcal://
example:

webcal://example.com/calendar.ics
HTTP as a transport protocol is assumed.
See Webcal
Webcal
webcal is an unofficial Uniform Resource Identifier scheme for accessing iCalendar files. It is also the name of two web calendar applications written in Perl....

 for details.
ws
wss
WebSocket protocol IETF Draft ws:
wtai Wireless Telephony Application Interface WAP Forum wtai://wp/mc/+18165551212 See Application Protocol Wireless Application Environment Specification Version 1.1 for details.
wyciwyg What You Cache Is What You Get WYCIWYG
WYCIWYG
WYCIWYG is an acronym that stands for What You Cache Is What You Get, commonly displayed in the address bar of Gecko-based Web browsers like Mozilla Firefox as wyciwyg:// when the Web browser is retrieving cached information.-Usage:Mozilla Firefox implements a unique, strictly internal wyciwyg://...

Mozilla
Mozilla
Mozilla is a term used in a number of ways in relation to the Mozilla.org project and the Mozilla Foundation, their defunct commercial predecessor Netscape Communications Corporation, and their related application software....

wyciwyg:// See WYCIWYG
WYCIWYG
WYCIWYG is an acronym that stands for What You Cache Is What You Get, commonly displayed in the address bar of Gecko-based Web browsers like Mozilla Firefox as wyciwyg:// when the Web browser is retrieving cached information.-Usage:Mozilla Firefox implements a unique, strictly internal wyciwyg://...

 for details.
xfire Adding friends and servers, joining servers, changing status text. Xfire
Xfire
Xfire is a proprietary freeware instant messaging service for gamers, that also serves as a game server browser and has various other features. It is currently available for Microsoft Windows. Xfire was originally developed by Ultimate Arena based in Menlo Park, California...

xfire:[?=[&=]] Official documentation from Xfire website
xri eXtensible Resource Identifier (XRI) OASIS
OASIS (organization)
The Organization for the Advancement of Structured Information Standards is a global consortium that drives the development, convergence and adoption of e-business and web service standards...

 XRI Technical Committee
xri://[/[]][?][#fragment] Official documentation from OASIS XRI Technical Committee
ymsgr Sending an instant message to a Yahoo! Contact. Yahoo! Messenger
Yahoo! Messenger
Yahoo! Messenger is an advertisement-supported instant messaging client and associated protocol provided by Yahoo!...

ymsgr:sendIM?

External links