Help: CS1 errors

==<span id="bad_url">Check |url= value</span>==
<section begin="bad_url_help_text" />{{help desk}}{{plainlist|
*{{#invoke:Cs1 documentation support|help_text_error_messages|err_bad_url|$1=<code class="cs1-code">{{pipe}}url=</code>}}
*{{#invoke:Cs1 documentation support|help_text_error_messages|err_bad_url|$1=<code class="cs1-code">{{pipe}}archive-url=</code>}}}}

External links in {{cs1}} and {{cs2}} templates are made from two parts: the ''title'' ({{para|title}}, {{para|chapter}}, etc.) and the ''URL'' ({{para|url}}, {{para|archive-url}}, {{para|chapter-url}}, etc.). The {{para|url}} parameter and other URL parameters must begin with a supported [[URI scheme]]. The URI schemes <code>http://</code>, <code>https://</code>, and the protocol relative scheme <code>//</code> are most commonly used; <code>irc://</code>, <code>ircs://</code>, <code>ftp://</code>, <code>news:</code>, <code>mailto:</code> and <code>gopher://</code> are also supported.

The URL scheme and host are checked to ensure that they contain only Latin characters, certain (required) punctuation, and do not contain spaces.  The URL may be protocol relative (begins with <code>//</code>).  If there are no spaces and the URL is not protocol relative, then the scheme must comply with <nowiki>RFC 3986</nowiki>.<ref>{{citation |mode=cs1 |contribution-url=http://tools.ietf.org/html/std66#section-3.1 |contribution=Scheme |title=Uniform Resource Identifier (URI): Generic Syntax |publisher=[[Internet Engineering Task Force]] |date=January 2005 |rfc=3986}}</ref>

Some URL domains are written with non-Latin characters.  cs1|2 does not accept those kinds of URLs so they must be '[[Internationalized domain name|internationalized]]'.  Online tools are available to internationalize URLs that are written in non-Latin scripts:
* {{cite web |url=https://www.verisign.com/en_US/channel-resources/domain-registry-products/idn/idn-conversion-tool/index.xhtml?loc=en_US |title=IDN Conversion Tool |website=Verisign }}

Top- and second-level domain names are checked for proper form.  Generally, top-level domain names must be two or more letters; second-level domain names must be two or more letters, digits, or hyphens (first and last character must be a letter or digit).  [[Single-letter second-level domain]]s are supported for:
* all [[Country code top-level domain|cc TLD]]s (the country code is not validated)
* the [[.org]] [[TLD]]
* certain letters of the [[.com]] TLD (q, x, z)
* certain letters of the [[.net]] TLD (i, q)
* certain other TLDs ({{#invoke:cs1 documentation support|single_ltr_2nd_lvl_domain_lister}})
Third- and subsequent-level domain names are not checked.  The path portion of the URL is not checked.

There is an additional test for {{para|archive-url}}.  The cs1|2 templates expect that {{para|archive-url}} will hold a unique URL for an archived snapshot of the source identified by {{para|url}} or {{para|chapter-url}} (or any of its aliases).  This error message is emitted when the value assigned to {{para|archive-url}} is the same as the matching title or chapter URL.  

To resolve this error, ensure that:
*{{para|url}} and other URL parameters contain valid URLs
*URLs copy-pasted from elsewhere include the URI scheme
*that the domain name uses only Latin characters

Pages with this error are automatically placed in {{#invoke:cs1 documentation support|help_text_cats|err_bad_url|pages=yes}}.<ref group="lower-alpha" name="categories" /><section end="bad_url_help_text" />
Description	What you type	What you get
Italic	''Italic text''	Italic text
Bold	'''Bold text'''	Bold text
Bold & italic	'''''Bold & italic text'''''	*Bold & italic text*
Description	What you type	What you get
Reference	Page text.<ref>[https://www.example.org/ Link text], additional text.</ref>	Page text.^[1]
Named reference	Page text.<ref name="test">[https://www.example.org/ Link text]</ref>	Page text.^[2]
Additional use of the same reference	Page text.<ref name="test" />	Page text.^[2]
Display references	<references />	↑ Link text, additional text. ↑ Link text