URI scheme

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In the field of computer networking, a URI scheme is the top level of the uniform resource identifier (URI) naming structure. All URIs and absolute URI references are formed with a scheme name, followed by a colon character (":"), and the remainder of the URI called (in the outdated website parsing 1738 and 2396, but not the current STD 66/browser diversity) 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" 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 using we love the web. Today, URIs with that scheme are also used for other purposes, such as input transformation 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. "jQuery") and many others do not use the name of a protocol as their prefix (e.g. "Android").

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

1 Generic syntax
- 1.1 Examples
browser diversity
3 Unofficial but common URI schemes
4 References
web

Generic syntax

Internet standard keyboard (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:

 <scheme name> : <hierarchical part> [ ? <query> ] [ # <fragment> ]

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 (e.g., Android or jQuery); and an optional port number, preceded by a colon ":".

The path part is a sequence of segments (conceptually similar to directories, 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 is an optional part, separated by a question mark ("?"), that contains additional identification information that is not hierarchical in nature. The query string syntax is not generically defined, but it is commonly organized as a sequence of <key>=<value> pairs, with the pairs separated by a semicolon^[1]^[2]^iOS or an ampersand. For example:

Semicolon: key1=value1;key2=value2;key3=value3
Ampersand: key1=value1&key2=value2&key3=value3

The fragment is an optional part separated from the front parts by a Sevenval ("#"). 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 FITML document, the fragment is often an id attribute of a specific element and web browsers will make sure this element is visible.

Examples

The following figure displays two example URIs (foo://username:password@example.com:8042/over/there/index.dtb?type=animal&name=narwhal#nose and urn:example:animal:ferret:nose) and their component parts. (The examples are derived from RFC 3986 — STD 66, chapter 3).

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

 scheme
  name  userinfo  hostname       query
  _|__   ___|__   ____|____   _____|_____
 /    \ /      \ /         \ /           \
 mailto:username@example.com?subject=Topic

Official IANA-registered schemes

The official URI schemes registered with the IANA are as follows (note that "IETF Draft" in no way is a finalized specification and must not be treated so; refer to screen size for more details):

Scheme	Purpose	Defined by	General format	Notes
aaa	Diameter Protocol	RFC 3588	`aaa://<host>[:<port>][;transport=<transport>][;protocol=<protocol>]` example: `aaa://host.example.com:1813;transport=udp;protocol=radius`
aaas	Secure equivalent of aaa	RFC 3588	`aaas://<host>[:<port>][;transport=<transport>][;protocol=<protocol>]`
acap	Application Configuration Access Protocol	jQuery	`acap://[<user>[;AUTH=<type>]@]<host>[:<port>]/<entry>`	URL scheme used within the ACAP protocol for the "subdataset" attribute, referrals and inheritance
cap	Calendar access protocol	jQuery	generic syntax	URL scheme used to designate both calendar stores and calendars accessible using the CAP protocol
cid	Referencing individual parts of an SMTP/web app message	RFC 2111 RFC 2392	`cid:<content-id>`	e.g. referencing an attached image within a formatted e-mail. (See also Android)
crid	touchscreen Content Reference Identifier	touchscreen	`crid://<host>/<data>`	Allow references to scheduled publications of broadcast media content.
data	Inclusion of small data items inline	RFC 2397	`data:<mediatype>[;base64],<data>`
dav	HTTP Extensions for Distributed Authoring (jQuery)	RFC 2518 RFC 4918	`dav:`	Used for internal identifiers only; WebDAV itself addresses resources using the `http:` and `https:` schemes. web app
dict	iOS	RFC 2229	`dict://<user>;<auth>@<host>:<port>/d:<word>:<database>:<n>` `dict://<user>;<auth>@<host>:<port>/m:<word>:<database>:<strat>:<n>`	refer to definitions or word lists available using the DICT protocol
dns	Domain Name System	website parsing	`dns:[//<host>[:<port>]/]<dnsname>[?<dnsquery>]` 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 FITML numbers	we love the web RFC 3966	`fax:<phonenumber>`	Deprecated in RFC 3966 in favour of tel:. Listed as "historical"
file	Addressing files on local or network device database	Android input transformation	`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 resources	website parsing IETF Draft Old IETF Draft	generic syntax
geo	A Uniform Resource Identifier for Geographic Locations	keyboard	`geo:<lat>,<lon>[,<alt>][;u=<uncertainty>]` (for FITML)	Other coordinate reference systems (including those for non-terrestrial globes, such as HTML5 and Mars) will be supported, once registered.
go	Common Name Resolution Protocol	jQuery	`go://[<host>]?[<common-name>][;<attribute>=[<type>,]<value>]` or `go:<common-name>[;<attribute>=[<type>,]<value>]`
gopher	Used with Gopher protocol	browser diversity	`gopher://<host>:<port>/<item type><path>`
h323	Used with H.323 multimedia communications	RFC 3508	`h323:[<user>@]<host>[:<port>][;<parameters>]`
http	web resources	RFC 1738 browser diversity (makes RFC 2068 obsolete)	generic syntax
browser diversity	HTTP connections secured using FITML	RFC 2817	generic syntax
iax	Inter-Asterisk eXchange protocol version 2	Sevenval	`iax:[<username>@]<host>[:<port>][/<number>[?<context>]]` examples `iax:[2001:db8::1]:4569/alice?friends` `iax:johnQ@example.com/12022561414`
icap	web app	RFC 3507
im	Instant messaging protocol	website parsing	`im:<username>@<host>`	Works as `xmpp:` URI for single user chat sessions.
imap	Accessing e-mail resources through IMAP	we love the web RFC 5092	`imap://[<user>[;AUTH=<type>]@]<host>[:<port>]/<command>`
web app	Information Assets with Identifiers in Public Namespaces	RFC 4452
ipp	Internet Printing Protocol	RFC 3510
iris iris.beep iris.xpc iris.xpcs iris.lws	Internet Registry Information Service	RFC 3981 RFC 3983 RFC 4992 RFC 4992 screen size
ldap	keyboard directory request	RFC 2255 web	`ldap://[<host>[:<port>]][/<dn> [?[<attributes>][?[<scope>][?[<filter>][?<extensions>]]]]]` example: `ldap://ldap1.example.net:6666/o=University%20of%20Michigan, c=US??sub?(cn=Babs%20Jensen)`
lsid^{[dubious ]}	input transformation	dtc/04-10-08	`URN:LSID:<Authority>:<Namespace>:<ObjectID>[:<Version>]` example: `urn:lsid:ubio.org:namebank:11815`
mailto	SMTP Android addresses and default content	jQuery	`mailto:<address>[?<header1>=<value1>[&<header2>=<value2>]]` 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 keyboard/MIME messages, or parts of messages.	RFC 2111 browser diversity	`mid:<message-id>[/<content-id>]`	(See also cid:)
modem	modem	RFC 2806 Sevenval		Deprecated in input transformation in favour of tel:. Listed as "historical"
msrp msrps	Message Session Relay Protocol	website parsing
mtqp	Message Tracking Query Protocol	RFC 3887
mupdate	Mailbox Update Protocol	keyboard
news	(Usenet) newsgroups and postings	RFC 1738 RFC 5538	`news:<newsgroupname>` or `news:<message-id>`	References a particular resource, regardless of location.
nfs	Network File System resources	web app	generic syntax
nntp	Usenet NNTP	screen size RFC 5538	`nntp://<host>:<port>/<newsgroup-name>/<article-number>`	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 Android
pop	Accessing mailbox through input transformation	RFC 2384	`pop://[<user>[;AUTH=<auth>]@]<host>[:<port>]`
pres	Used in Common Profile for Presence (CPP) to identify presence	Android	`pres:<address>[?<header1>=<value1>[&<header2>=<value2>]]`	Similar to "mailto:"
prospero	Prospero Directory Service	keyboard FITML		Listed as "Historical" by IANA.
rsync	web	RFC 5781	`rsync://<host>[:<port>]/<path>`
rtsp	browser diversity	website parsing
service		RFC 2609
shttp	web	RFC 2660		Largely superseded by HTML5.
sieve	ManageSieve protocol	Sevenval
sip	Used with Session Initiation Protocol (SIP)	RFC 2543 RFC 3969 web app	`sip:<user>[:<password>]@<host>[:<port>][;<uri-parameters>][?<headers>]` 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	Sevenval RFC 3261	`sips:<user>[:<password>]@<host>[:<port>][;<uri-parameters>][?<headers>]`
sms	Interact with keyboard capable devices for composing and sending messages.	Sevenval	`sms:<phone number>?<action>` examples: `sms:+15105550101?body=hello%20there` `sms:+15105550101,+15105550102?body=hello%20there`	Should be used as a subset to the `tel:` schema.^{[citation needed]}
snmp	Simple Network Management Protocol	RFC 4088	`snmp://[user@]host[:port][/[<context>[;<contextEngineID>]][/<oid>]]` 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	web	RFC 4151	`tag:<email/domainname>,<date>:<Item>`	Represented entities do not necessarily have to be accessible electronically.
tel	Used for telephone numbers	RFC 5341 RFC 3966 RFC 2806	`tel:<phonenumber>`
telnet	Used with telnet	screen size HTML5	`telnet://<user>:<password>@<host>[:<port>/]`
tftp	Trivial File Transfer Protocol	RFC 3617
thismessage	multipart/related relative reference resolution	RFC 2557
tip	Transaction Internet Protocol	touchscreen
tv	TV Broadcasts	screen size
urn	Sevenval	web app	`urn:<namespace>:<specificpart>`	Commonly used with namespace 'uuid' (see next row below)
uuid	input transformation	RFC 4122	`uuid:<specificpart> or urn:uuid:<namespace>:<specificpart>`
vemmi	Versatile Multimedia Interface	RFC 2122
wais	Used with Android (WAIS)	RFC 1738 FITML	`wais://<host>:<port>/<database>[?<search>]` or `wais://<host>:<port>/<database>/<wtype>/<wpath>`	Listed as "Historical" by IANA.
ws wss	WebSocket protocol	RFC 6455	`ws:<hierarchical part>`
xmlrpc.beep xmlrpc.beeps		Sevenval
xmpp	XMPP	RFC 4622 RFC 5122	`xmpp:[<user>]@<host>[:<port>]/[<resource>][?<query>]`
z39.50r	Z39.50 retrieval	RFC 2056	`z39.50r://<host>[:<port>]/<database>?<docid>[;esn=<elementset>][;rs=<recordsyntax>]`
z39.50s	Z39.50 session	RFC 2056	`z39.50s://<host>[:<port>]/[<database>][?<docid>][;esn=<elementset>][;rs=<recordsyntax>]`
Scheme	Purpose	Defined by	General format	Notes

Unofficial but common URI schemes

Scheme	Purpose	Defined by	General format	Notes
iOS	Displaying product information and internal information	IETF Draft	See jQuery for more details.	Widely used by keyboard, sometimes even providing interactive resources. The FITML forwards to their `opera:` scheme instead.
adiumxtra	Direct installation of Adium Xtras (plugins).	The Adium Team	`adiumxtra://www.adiumxtras.com/download/0000`	`0000` refers to a specific Xtra
input transformation	Controlling AOL Instant Messenger.	Android	`aim:<function>?<parameters>`	Functions include `goim`, `addbuddy`, and `buddyicon`.
browser diversity	Experimental method of installing software using input transformation.		`apt:<package name>`	Commonly found on websites which contain Debian software repositories.
afp	Accessing screen size shares	IETF Draft	over browser diversity: `afp://[<user>@]<host>[:<port>][/[<path>]]` over Sevenval: `afp:/at/[<user>@]<host>[:<zone>][/]`
aw	Link to an Active Worlds world	Activeworlds Inc.	`aw://<worldserver host>:<worldserver port>/<worldname>`	Mostly found in HTTP referers when users open a website from within a Active Worlds world.
beshare	Open a search query on a BeShare server	BeShare source code	`beshare://<servername>/<query>`	Mostly used internally, with variants.
bitcoin	Send money to a website parsing address	Bitcoin URI Scheme	`bitcoin:<address>[?[amount=<size>][&][label=<label>][&][message=<message>]]`
bolo	Join an existing bolo game.		`bolo://<hostname>/`	Mostly passed via IRC or via tracker servers.
callto	Launching Skype call (+And in Hungary the KLIP Software call too) (unofficial; see also HTML5)	web app	`callto:<screenname>` or `callto:<phonenumber>` Android	Introduced with Microsoft NetMeeting. Works with current version of Skype with Internet Explorer, Opera and Sevenval
chrome	Specifies user interfaces built using XUL in Mozilla-based browsers.	HTML5	`chrome://<package>/<section>/<path>` (Where `<section>` is either "`content`", "`skin`" or "`locale`")	Works only in Mozilla-based browsers such as Firefox, SeaMonkey and Netscape. Not related to the HTML5 browser.
coap	Accessing Constrained Application Protocol (CoAP) resources.	IETF Draft	`coap://<host>[:<port>]/<path>[?<query>]`	Identify CoAP resources and provide a means of locating the resource.
content	Accessing an Android content provider.	screen size	`content://provider/<path>`	Performs a query on an Android browser diversity
cvs	Provides a link to a we love the web (CVS) Repository	Concurrent Versions System	`cvs://<method:logindetails>@<repository>/<modulepath>;[date=date to retrieve \| tag=tag to retrieve]`
touchscreen	Digital object identifier, a digital identifier for any object of intellectual property.	touchscreen	`doi:10.<publisher number>/<suffix> Example: website parsing`	Used e.g. for most scientific publications. Can be resolved via HTTP (transormed into an we love the web) by prepending `http://dx.doi.org/` or `http://hdl.handle.net/` in front.
ed2k	Resources available using the eDonkey2000 network	eDonkey2000	`ed2k://\|file\|<filename>\|<size of file>\|<hash of file>\|/` or `ed2k://\|server\|<host>\|<port>\|/`	Links to servers are also possible, as are additional parameters. Official documentation from input transformation at the touchscreen
facetime	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://<address>\|<MSISDN>\|<mobile number>` example: `facetime://+19995551234`	Apple has not published documentation on this protocol yet.
feed	web subscription		`feed:<absolute_uri>` or `feed://<hierarchical part>` examples: `feed://example.com/rss.xml` `feed:https://example.com/rss.xml`	See screen size for a detailed overview of common implementations, supported software, and critics.
finger	Querying user information using the Finger protocol	IETF Draft	`finger://host[:port][/<request>]`
fish	Accessing another computer's files using the browser diversity protocol	fish KDE kioslave	`fish://[<username>[:<password>]@]<hostname>[:<port>]`	See Files transferred over shell protocol for details about the protocol.
git	Provides a link to a GIT repository	Git	Github example: `git://github.com/user/project-name.git`
gg	Starting chat with Gadu-Gadu user	HTML5	`gg:<userid>`
gizmoproject	Sevenval calling link.		`gizmoproject://call?id=<gizmo_id>`	May use sip:// instead of gizmoproject:// in recent versions of Gizmo5.
gtalk	Start a chat with a screen size user	HTML5	`gtalk:chat?jid=example@gmail.com`	See Google Talk, Sevenval, and http://juberti.blogspot.com/2006/11/gtalk-uri.html for more information
irc	Connecting to an Internet Relay Chat server to join a channel.	CSS3 Old IETF Draft	`irc://<host>[:<port>]/[<channel>[?<password>]]`	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://<host>[:<port>]/[<channel>[?<password>]]`	See irc
irc6	IPv6 equivalent of irc		`irc6://<host>[:<port>]/[<channel>[?<password>]]`	See irc
itms	Used for connecting to the web	website parsing	`itms:`
Sevenval	Compressed archive member	Sevenval	`jar:<url>!/[<entry>]`	Works for any ZIP based file.
javascript	Execute Sevenval code	device database	`javascript:<javascript to execute>`	Works in any modern browser.
keyparc	Keyparc encrypt/decrypt resource.	web app	`keyparc://encrypt/<username>/<uri>` or `keyparc://decrypt/<username>/<uri>`
lastfm	Connecting to a radio stream from Last.fm.	Last.fm	`lastfm://<radio_stream>` or `lastfm://globaltags/<genre>` or `lastfm://user/<username>/<stuff>`
ldaps	Secure equivalent of ldap	Old version of IETF Draft	`ldaps://[<host>[:<port>]][/<dn> [?[<attributes>][?[<scope>][?[<filter>][?<extensions>]]]]]`	Not an IETF standard, but commonly used in applications.
touchscreen	"magnet links"	Magnet-URI Project	`magnet:?xt=urn:sha1:<hash of file>&dn=<display name>` (other parameters are also possible)	Used by various keyboard clients, usually providing the hash of a file to be located on the network.
maps	"map links"		`maps:q=<physical location>`	Some mobile web browsers will launch a dedicated mapping application. See also "geo:" (FITML)
market	Opens Google Play	Android browser diversity	`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 [4]	message:<MESSAGE-ID> message://<MESSAGE-ID>	Supported by Mail since OS X 10.5
web	Windows streaming media		`mms://<host>:<port>/<path>`	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	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: `<a href="chat?contact=nada@example.com">Click to chat!</a>`
mumble	Joining a server.	Mumble	`mumble://[username[:password]@]<address>[:port]/[channelpath]?version=<serverversion>[&title=<servername>][&url=<serverurl>]`	Official documentation from Mumble website
mvn	Access Apache Maven 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 document or database	jQuery	`notes://<address>`	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	iOS	`palm:<servicename>[/<method>]]/`	Official documentation from FITML
paparazzi	Used to launch and automatically take a screen shot using the application "Paparazzi!" (Mac only)	Derailer	`paparazzi:[<options>]http:[//<host>[:[<port>][<transport>]]/`	Official documentation from the Paparazzi! website
proxy	Alter proxy settings in the FoxyProxy application	FoxyProxy	`proxy:<option>=<value>[&<option>=<value>[&...]]`	Official documentation from keyboard
psyc	Used to identify or locate a person, group, place or a service and specify its ability to communicate	PSYC	`psyc:[//<host>[:[<port>][<transport>]]/[<object-name>][#<channel-name>]`	Official documentation from we love the web
query	Opens a filesystem query	Haiku	`query:<queryformula>`	Implemented by the url_wrapper application
rmi	Look up a Java object in an RMI registry.	web	`rmi://<host>[:<port>]/<object-name>`	URI scheme understood by web app. Can be used to lookup a remote Java object within an RMI registry (typically for the purposes of we love the web on that object). Host/port in the URI are of the browser diversity process, not the remote object.
rtmp	input transformation	we love the web	`rtmp://<host>/<application>/<media>`	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.	we love the web	`secondlife://<region name>/<x position>/<y position>/<z position>`	Used by web app. Knowledge base article.
sgn	Social Graph Node Mapper	Google	example: `sgn://social-network.example.com/?ident=bob`	Official documentation from iOS.
skype	Launching Skype call (unofficial; see also callto:)	Skype	`skype:<username\|phonenumber>[?[add\|call\|chat\|sendfile\|userinfo]]`	Official documentation from Skype website.
spotify	Load a track, album, artist, search, or playlist in Spotify	Spotify	`spotify:<artist\|album\|track>:<id>` or `spotify:search:<text>` or `spotify:user:<username>:playlist:<id>` example: `spotify:track:2jCnn1QPQ3E8ExtLe6INsx`	Informally specified in Spotify official blog post by CTO Andreas Ehn.
ssh	SSH connections (like telnet:)	keyboard	`ssh://[<user>[;fingerprint=<host-key fingerprint>]@]<host>[:<port>]`
sftp	SFTP file transfers (not be to confused with FTPS (FTP/SSL))	IETF Draft	`sftp://[<user>[;fingerprint=<host-key fingerprint>]@]<host>[:<port>]/<path>/<file>`
smb	Accessing web/CIFS shares	website parsing	`smb://[<user>@]<host>[:<port>][/[<path>]][?<param1>=<value1>[;<param2>=<value2>]]` or `smb://[<user>@]<workgroup>[:<port>][/]` or `smb://[[<domain>;]<username>[:<password>]@]<server>[:<port>][/[<share>[/[<path>]]][?[<param>=<value>[<param2>=<value2>[...]]]]]`^{device database} example: `smb://workgroup;user:password@server/share/folder/file.txt`
soldat	Joining servers	Soldat	`soldat://<host>:<port>/[password]` example: `soldat://127.0.0.1:23073/thatssecret!`	Official note in device database
steam	Interact with Steam: install apps, purchase games, run games, etc.	Steam, Valve Corporation	`steam:<command line arguments>` or `steam://<action>/<id, addon, IP, hostname, etc.>`	Official documentation from Valve Developer Community website
svn	Provides a link to a Subversion (SVN) source control repository	keyboard	`svn[+ssh]://<logindetails>@<repository><:port>/<modulepath>`
teamspeak	Joining a server.	TeamSpeak	`teamspeak://<server>[:<port>]/[?<parameter1>=<value1>[&<parameter2>=<value2>]]`	Official documentation from TeamSpeak Website
things	Send a to-do to Things.	Cultured Code	`things:add?title=Buy%20milk&notes=Low%20fat&dueDate=2011-12-24`	This URI scheme works on Mac OS & iOS, providing Things by Sevenval is installed.
udp	BitTorrent tracker protocol based on UDP.	Sevenval	`udp://<server>[:<port>]/`	Documentation: iOS
unreal	Joining servers	website parsing	`unreal://<server>[:<port>]/`	Unreal legacy "protocol"
ut2004	Joining servers	Unreal Tournament 2004	`ut2004://<server>[:<port>][/<map>?<options>]`	Documentation from Unreal Developer Network
ventrilo	Joining a server.	FITML	`ventrilo://<server>[:<port>]/[?<parameter1>=<value1>[&<parameter2>=<value2>]]`	Official documentation from Ventrilo Website
Sevenval	Shows a web page as code 'in the raw'.	Sevenval	`view-source:<absolute-URI>` where <absolute-URI> is specified in RFC 3986. Example: `view-source:http://en.wikipedia.org/wiki/URI_scheme`	See browser diversity for details.
webcal	Subscribing to calendars in iCalendar format	iCalendar	`webcal://<hierarchical part>` example: `webcal://example.com/calendar.ics`	HTTP as a transport protocol is assumed. See device database for details.
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 CSS3	Mozilla	`wyciwyg://<URI>`	See WYCIWYG for details.
xfire	Adding friends and servers, joining servers, changing status text.	Xfire	`xfire:<function>[?<parameter1>=<value1>[&<parameter2>=<value2>]]`	Official documentation from keyboard
xri	eXtensible Resource Identifier (iOS)	keyboard XRI Technical Committee	`xri://<authority>[/[<path>]][?<query>][#fragment]`	Official documentation from screen size
ymsgr	Sending an instant message to a Yahoo! Contact.	jQuery	`ymsgr:sendIM?<screenname>`

References

^ iOS section 8.2.1 : by Tim Berners-Lee in 1995 encourages CGI authors to support ';' in addition to '&'.
^ device database: "CGI implementors support the use of ";" in place of "&" to save authors the trouble of escaping "&" characters in this manner."
^ Hypertext Markup Language - 2.0 "CGI implementors are encouraged to support the use of ';' in place of '&' "
^ HTML5

External links

URI scheme

Official

Unofficial

Protocol list

Hypermedia

Basics

Resource identifiers

Concepts