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{{Short description|URI scheme for linking email addresses}}
{{confused|Malito}}
{{lowercase}}
'''mailto''' is a [[Uniform Resource Identifier]] (URI) scheme for [[email addresses]]. It is used to produce [[hyperlink]]s on [[websites]] that allow users to send an [[email]] to a specific address directly from an [[HTML]] document, without having to copy and enter it into an [[email client]]. 

It was originally defined by [[Request for Comments]] (RFC) 1738 in December 1994,<ref>{{cite web|url=https://tools.ietf.org/html/rfc1738|title=Uniform Resource Locators (URL)|author1-first=T.|author1-last=Berners-Lee|author2-first=Larry|author2-last=Masinter|author3-first=M.|author3-last=McCahill|date=December 1994|accessdate=11 September 2021}}</ref> expanded by <nowiki>RFC</nowiki> 2368 in July 1998,<ref>{{cite web|url=https://tools.ietf.org/html/rfc2368|title=The mailto URL scheme|author1-first=Paul|author1-last=Hoffman|author2-first=Larry|author2-last=Masinter|author3-first=Jamie|author3-last=Zawinski|author3-link=Jamie Zawinski|date=July 1998|accessdate=26 September 2015}}</ref> and refined by <nowiki>RFC</nowiki> 6068 in October 2010.<ref name="rfc6068">{{cite web|url=https://tools.ietf.org/html/rfc6068|title=The 'mailto' URI Scheme|author1-first=Martin|author1-last=Duerst|author2-first=Larry|author2-last=Masinter|author3-first=Jamie|author3-last=Zawinski|author3-link=Jamie Zawinski|date=October 2010|accessdate=26 September 2015}}</ref>

== Syntax ==
Mailto URIs are composed of the scheme <code>mailto:</code> and one or more recipient addresses separated with a comma. Additionally, email headers such as <code>cc</code> or <code>subject</code> can be added as [[attribute-value pairs]] in the query component of the email.

[[Percent-encoding]] must be used for the local-part of the Email addresses and for the header values. The Domain parts of the addresses can also be encoded using percent-encoding but using [[Internationalized domain name|IDNA-Encoding]] is recommended for interoperability with legacy software.<ref name="rfc6068" />

== Examples ==
"mailto" can be used within an [[HTML]] document to generate a link for sending email:
<syntaxhighlight lang="html"><a href="mailto:someone@example.com">Send email</a></syntaxhighlight>

Clicking on the hyperlink automatically opens the default email client, with the destination email address pre-filled.

It is possible to specify initial values for headers (e.g. subject, cc, etc.) and message body in the URL. Blanks, carriage returns, and line feeds cannot be directly embedded but must be [[Percent-encoding|percent-encoded]]:<ref>{{Cite web|url=https://developer.mozilla.org/en-US/docs/Learn/HTML/Introduction_to_HTML/Creating_hyperlinks|title=Creating hyperlinks § E-mail links|website=MDN Web Docs|language=en|access-date=2019-09-30}}</ref>
<syntaxhighlight lang="html"><a href="mailto:someone@example.com?subject=This%20is%20the%20subject&cc=someone_else@example.com&body=This%20is%20the%20body">Send email</a></syntaxhighlight>

Multiple addresses can be specified:<ref name="rfc6068"/>
<syntaxhighlight lang="html"><a href="mailto:someone@example.com,someoneelse@example.com">Send email</a></syntaxhighlight>

The address can be omitted:
<syntaxhighlight lang="html"><a href="mailto:?subject=mailto%20with%20examples&body=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FMailto">Share this knowledge...</a></syntaxhighlight>Only the initial header should be prepended with a [[question mark]]. All subsequent headers require an [[ampersand]]. If this convention is not followed, the scheme will not properly copy over the headers to the email client.<ref>{{Cite web|title=RFC 6068|url=https://datatracker.ietf.org/doc/html/rfc6068#section-6.1|website=IETF Datatracker}}</ref>

==Security and privacy==
{{see also|Address munging}}

A number of security issues are mentioned in [https://datatracker.ietf.org/doc/html/rfc6068#section-7 RFC 6068], one of them being robotic [[address harvesting]]. Mailto constructs are locatable within HTML pages by automated means which typically include the use of [[Document Object Model|DOM]] constructs or [[regular expression]]s. Addresses harvested by such means are liable to be added to [[E-mail spam|spam]]mers' mass-mailing lists and thus to receive large amounts of unwanted mail.

While methods exist to "harden" mailto links against harvesting—[[address munging]] and [[JavaScript]]-based address [[Obfuscation (software)|obfuscation]] among them—these protections can be circumvented by sufficiently sophisticated harvesting robots.  Other techniques, like walling the address behind a [[CAPTCHA]] or similar "humanity check", provide security on par with that available for other contact methods, most notably [[Form (HTML)|web forms]], which experience similar challenges with preventing spam.

== References ==
<references />
{{URI scheme}}

[[Category:Email]]
[[Category:URI schemes]]
[[Category:Web 1.0]]