CorporisPublica:Manual of Style/Linking

Linking through hyperlinks is an important feature of Wikipedia. Internal links bind the project together into an interconnected whole. Interwiki links bind the project to sister projects such as Wikisource, Wiktionary, and Wikipedia in other languages; and external links bind Wikipedia to the external World Wide Web.

Appropriate links provide instant pathways to locations within and outside the project that are likely to increase readers' understanding of the topic at hand. When writing or editing an article, it is important to consider not only what to put in the article, but what links to include to help the reader find related information, as well as which other pages should carry links to the article. Care should be taken to avoid both underlinking and overlinking, as described below.

This page provides guidelines as to when links should and should not be used, and how to format links. Detailed information about the syntax used to create links can be found at Help:Link. The rules on linking applicable to disambiguation pages are set out in the disambiguation style guide.

Principles
Wikipedia is based on hypertext, and aims to "build the web" to enable readers to easily access relevant information on other pages. The page from which the hyperlink is activated is called the anchor; the page the link points to is called the target.

In adding or removing links, consider an article's place in the knowledge tree. Internal links can add to the cohesion and utility of Wikipedia, allowing readers to deepen their understanding of a topic by conveniently accessing other articles. Ask yourself, "How likely is it that the reader will also want to read that other article?" Consider including links where readers might want to use them; for example, in article leads, at the openings of new sections, in the cells of tables, and in image captions. But note below that as a rule of thumb editors should only link the term's first occurrence in the text of the article.

General points on linking style

 * As explained in more detail at Help:Links, linking can be "direct" (, which results in Riverside, California), or "piped" ( , which results in Riverside in the text, but still links to the article "Riverside, California", though see Pipe trick for an easier way to create this particular link).
 * Section headings should not themselves contain links; instead, a main or seealso template should be placed immediately after the heading.
 * Links should not be placed in the boldface reiteration of the title in the opening sentence of a lead.
 * Items within quotations should not generally be linked; instead, consider placing the relevant links in the surrounding text or in the "See also" section of the article.
 * When possible, avoid placing links next to each other so that they look like a single link, as in  (Irish Chess Championship). Consider rephrasing the sentence, omitting one of the links, or using a more specific single link (e.g. to Irish Chess Championship) instead.
 * Articles on technical subjects might need a higher density of links than in general-interest articles, due to their larger number of technical terms that general dictionaries are unlikely to explain in context.
 * Do not create links to user or wikiproject pages in articles, except in articles about Wikipedia itself (see WP:Self-references to avoid).
 * Do not unnecessarily make a reader chase links: if a highly technical term can be simply explained with very few words, do so. Also use a link, but do not make a reader be forced to use that link to understand the sentence, especially if this requires going into nested links (a link that goes to a page with another technical term needed to be linked, which goes to a page with a link to another technical term, and so on). Don't assume that readers will be able to access a link at all, as, for example, they might have printed an article and be reading the hard copy on paper.

What generally should be linked
An article is said to be underlinked if words are not linked that are needed to aid understanding of the article. In general, links should be created to: Do not be afraid to create links to potential articles that do not yet exist (see Red links below).
 * relevant connections to the subject of another article that will help readers understand the article more fully (see the example below). This can include people, events and topics that already have an article or that clearly deserve one, so long as the link is relevant to the article in question.
 * articles with relevant information, for example: "see Fourier series for relevant background".
 * articles explaining technical terms, jargon or slang expressions—but you could also provide a concise definition instead of or in addition to a link. If there is no appropriate Wikipedia article, an interwiki link to Wiktionary could be used.
 * proper names that are likely to be unfamiliar to readers.

If you feel that a link does not belong in the body of an article, consider moving it to a "See also" section.

What generally should not be linked
An article is said to be overlinked if it contains an excessive number of links. Overlinking should be avoided, because it makes it difficult for the reader to identify and follow links that are likely to be of value. Unless they are particularly relevant to the topic of the article, avoid linking:
 * everyday English words that are expected to be understood in the general context;
 * the names of major geographic features and locations, languages, religions, common professions, and pre and post nominals;
 * units of measurement that aren't obscure and common (e.g. relating to: currency, data size, time, temperature, length, area, volume, etc.). If a metric and a non-metric unit are provided, as in 18 °C, there is no need to link either unit because almost all readers will understand at least one of the units;
 * dates (see below).

Do not link to pages that redirect back to the page the link is on (unless the link is to a redirect with possibilities that links to an appropriate section of the current article).

Generally, a link should appear only once in an article, but if helpful for readers, links may be repeated in infoboxes, tables, image captions, footnotes, and at the first occurrence after the lead.

Lead section
Too many links can make the lead hard to read. In technical articles that use uncommon terms, a higher-than-usual link density in the lead section may be necessary. In such cases, try to provide an informal explanation in the lead, avoiding using too many technical terms until later in the article—see WP:Make technical articles accessible and point 7 of WP:NOT.

An example article
For example, in the article on supply and demand:
 * almost certainly link "microeconomics" and "general equilibrium theory", as these are technical terms that many readers are unlikely to understand at first sight;
 * consider linking "price" and "goods" only if these common words have technical dimensions that are specifically relevant to the topic.
 * do not link to the "United States", because that is an article on a very broad topic with no direct connection to supply and demand.
 * definitely do not link "potato", because it is a common term with no particular relationship to the article on supply and demand, beyond its arbitrary use as an example of traded goods in that article.
 * Make sure that the links are directed to the correct articles: in this example, you should link good (economics), not good. Many common dictionary words link to disambiguation pages.

Link clarity
The article linked to should correspond to the term showing as the link as closely as possible given the context: for example, When Mozart wrote his Requiem rather than When Mozart wrote his Requiem, or Previn conducted Mozart's Requiem rather than Previn conducted Mozart's Requiem – this makes it clear the link is to the article on Mozart's Requiem in particular, rather than that on requiems in general. The link target and the link label do not have to correspond to each other, but the link must be as intuitive as possible. Thus, one may have a link "second longest European river" with the target 'Danube' and the link label 'second longest European river'. For further detail, refer to the section Piped links.

Link specificity
Always link to the article on the most specific topic appropriate to the context from which you link: it will generally contain more focused information, as well as links to more general topics. (Move your mouse pointer over the blue links in the table below to see the target.)

In each case the specific link is preferred.

If there is no article about the most specific topic, do one of the following things:
 * Consider creating the article yourself.
 * If an article on the specific topic does not yet exist, create a redirect page to the article about a more general topic, as described in section . For example, if no article yet exists on the song "Sad Statue" from the album Mezmerize, create a new article called Sad Statue that redirects to the article Mezmerize.
 * If there is no article on a more general topic either, then create a red link, but read below.

When neither a redirect nor a red link appear appropriate, consider linking to a more general article instead. For example, instead of Baroque hairstyles, write Baroque hairstyles, Baroque hairstyles, Baroque hairstyles, or hairstyles of the Baroque, depending on the context.

If an existing article has a section specifically about the topic, you can redirect or link directly to it, by appending a number sign and the name of the section to the article name. For example, Underpromotion is a redirect to Promotion (chess), and in the article Quark, the link eight gluon types (typed as ) links to a specific section in the article Gluon. When doing this, add a hidden comment to the target section such as  so that someone changing the title of that section can fix the incoming links. (Alternatively, use Template:Anchor in case of a large number of links to the section.)

To link to a section of the same article, e.g. in the lead of Promotion (chess), write:.

Redirects
Let's assume for example you needed a link "poodle", and there was no article for poodles yet. You might want to create a redirect from "poodle" to "dog" as follows: Write the link in the text as if the "poodle" article existed:. When you save or preview this, you will see: She owned a poodle. Click on the red link to create the redirect page, enter the target article name (in our case, Dog), select that text, and click the "#R" button. This will create the following text:.

The advantage of redirects over piped links is that they allow us to determine which pages link to the given topic using Special:WhatLinksHere, which in turn allows us to (There is currently no way to apply Whatlinkshere directly to article sections.)
 * create a new article when a significant number of links to that topic exist (see WP:Don't fix links to redirects that are not broken and Redirects with possibilities)
 * maintain links, e.g. by filtering incoming links and identifying related articles.

To link to a redirect page without following the underlying redirect, use, replacing PageName with the name of the redirect page to link.

Piped links
You may want to display a text for a link that is different from the linked article title. This can be achieved with what is called Piped links. Example:, which displays as Henry II. However, make sure that it is still clear what the link refers to without having to follow the link. Think about what the reader will believe the link is about. Example: When you use a link such as (which displays as Archery), the reader will expect this link to go to a general article on archery, rather than Archery at the 2008 Summer Olympics. The exception is when it is clear from the context that links go to specific articles, as in template:2008 Summer Olympics calendar, where all links go to the article about these specific games.
 * Plurals and other derived names. When forming plurals, you can do so thus: which includes the final "s" in the link like this: apples. This is easier to type and clearer to read in the source text than . This works not just for "s", but for any words that consist of an article name and some additional letters. For details, see Help:Link. (This does not work for affixes beginning with hyphens, apostrophes, or capital letters.)
 * Case sensitivity. Links are not sensitive to initial capitalization, so there is no need to use piping where the only difference between the text and the target is the case of the initial letter (Wikipedia article titles almost always begin with a capital, whereas the linked words in context often do not). However, links are case-sensitive for all but the initial character.


 * Intuitiveness. Keep piped links as intuitive as possible. Per the Principle of least astonishment, make sure that the reader knows what to expect when clicking on a link. You should plan your page structure and links so that everything appears reasonable and makes sense. If a link takes readers to somewhere other than where they thought it would, it should at least take them somewhere that makes sense. For example, do not write this:




 * The readers will not see the hidden reference to the parton model unless they click on or hover over the piped particle physics link; in hard copy, the reference to partons is completely lost. (Such links are sometimes called Easter eggs.) Instead, reference the article with an explicit "see also" or by rephrasing:


 * Richard Feynman was also known for work in (he proposed the   model).


 * Piping and redirects. Per above, do not use a piped link where it is possible to use a redirected term that fits well within the scope of the text. For example, let's assume the page A Dirge for Sabis is a redirect to the page The Sword of Knowledge, and while you're editing some other article, you want to add a link to A Dirge for Sabis. You may be tempted to avoid the redirect by directly linking to it with a pipe like this: . Instead, write simply  and let the system handle the rest. This has the added advantage that if an article is written later about the more specific subject (in this case, A Dirge for Sabis), fewer links will need to be changed to accommodate for the new article.

Piped links to sections of articles
Linking to particular sections of articles can be useful, inasmuch as it can take the reader immediately to the information that is most focused on the original topic. If you decide not to use a redirect, you have to use a piped link, because the format "Article name#Section name", is not good enough for display in an article. The format for a subsection link is. Please note, section name is case sensitive. For example, to link to the "Culture" subsection of the Oman article, type (which displays as culture of Oman). When doing this, add a hidden comment to the target section such as  so that someone changing the title of that section can fix the incoming links. (Alternatively, use in case of a large number of links to the section.) Among topics useful for linking to, there are many which Wikipedia currently implements as article sections, but which are potentially notable enough to become standalone articles. For example, the article Eastern Anyshire can have a small ==History== section, but this does not preclude an article on the History of Eastern Anyshire to be eventually written. Usually, a redirect page from a sub-topic to a general topic already exists, or should be created on demand. It is bad practice to make such links as Article#Section links explicitly, because navigation becomes inconvenient after the section is replaced by a summary of a new article. Instead, link through redirects, as it costs little and makes improvements easier.

See also Section linking help.

Links to Wikipedia's categories
Wikipedia has categories of articles like ; adding this to an article puts it into that category. You can link to a category by putting a colon in front.

For example links to Category:Phrases, and piping can be used: Phrases.

creates:

Red links
An internal link that displays in red points to a page that does not exist by that name. Some red links come about due to errors (misspelling, or failure to check the exact name of the target article); these should be fixed by correcting the spelling, using a piped link or, if appropriate, creating a redirect. However, many red links are perfectly legitimate, serving to point to an article which may exist in the future, and indeed encouraging editors to create such an article.

Legitimate red links should not be resolved simply by delinking (by removing the brackets). If a red link is within the context of the article, and it is a topic with the potential to eventually be a neutral, verifiable and encyclopedic article, then the link should be kept. Such links do not have an expiration date, beyond which they must be "fixed". Red links should be removed only if they point to articles that are unlikely ever to be created, such as the names of book chapters, or if they would have little significance in the context of the present article even if they were created.

Red is only the default color for these links for logged-in users, who can change their preferences to select another color.

To make a link more useful to readers when no article currently exists, it may be useful to create a redirect to a relevant existing article or section, or to create a stub for the new article (check similar articles for conventions on naming and categorization).

Checking links as they are created
One of the most common errors in linking occurs when editors do not check to see whether a link they have created goes to the intended location. This is especially true when a mistake is not obvious to the reader or to other editors. The text of links needs to be exact, and many Wikipedia destinations have a number of similar titles. To avoid such problems, which can be irritating for readers, the following procedure is recommended, especially for editors who are new to creating links.
 * 1) Carefully key in the link.
 * 2) Click on "Show preview".
 * 3) In the display-mode, click on the links (or open them in a new browser tab) to check they go where you intend; if they do not, fix them. If a destination page does not appear to exist, do a quick search to determine whether the article has a differently worded title or the subject is treated in a section of another article. Adjust the link accordingly or leave it as a red link.
 * 4) Return to the "Show preview" page using your browser's return button (or close the browser tab showing the linked article).
 * 5) Click on "Save page".

By following naming conventions, an internal link will be much more likely to lead to an existing article. When there is not yet an article about the subject, a good link will make the creation of a correctly named article much easier for subsequent writers.

Month-and-day linking
Month-and-day articles (e.g. February 24 and July 10) should not be linked unless their content is relevant and appropriate to the subject. Such links should share an important connection with that subject other than that the events occurred on the same date. For example, editors should not link the date (or year) in a sentence such as (from Sydney Opera House): "The Sydney Opera House was made a UNESCO World Heritage Site on 28 June 2007", because little, if any, of the contents of either June 28 or 2007 are germane to either UNESCO, a World Heritage Site, or the Sydney Opera House. References to commemorative days (Saint Patrick's Day) are treated as for any other link.

Intrinsically chronological articles (1789, January, and 1940s) may themselves contain linked chronological items.

Year linking
Year articles (e.g. 1795, 1955, 2007) should not be linked unless they contain information that is relevant and topical to the subject matter—that is, the events in the year article should share an important connection other than merely that they occurred in the same year. For instance, Timeline of World War II (1942) may be linked to from another article about WWII, and so too may 1787 in science when writing about a particular development on the metric system in that year. However, the years of birth and death of architect Philip C. Johnson should not be linked, because little, if any, of the contents of 1906 and 2005 are germane to either Johnson or to architecture.

Intrinsically chronological articles (1789, January, and 1940s) may themselves contain linked chronological items.

Units of measurement that aren't obscure
Units should generally only be linked to if they are likely to be obscure to readers of the article, or if they are being discussed (see use–mention distinction). So, for example, the troy ounce or bushel, the candela or mho might be considered obscure. Units that are relatively common generally don't need to be linked. Other units may be obscure in some countries, but well known in others (such as metric system units, which are not well known in the US) and so linking them may be useful, unless a conversion is present, as in 20 C or 68 F (since practically all readers will understand at least one of the measures).

External links section
Wikipedia is not a link collection, and an article comprising only links is contrary to what the "what Wikipedia is not" policy dictates.

Syntax
The syntax for referencing a URL is simple. Just enclose it in single brackets with a space between the URL and the text that will be displayed when the page is previewed or saved:

The text will display as:
 * Text to display

The URL must begin with  or another common protocol, such as   or. If no protocol is used, the square brackets will display normally – [like this] – and can be used in the standard way.

In addition, putting URLs in plain text with no markup automatically produces a link, for example  → http://www.example.org/. However, this feature may disappear in a future release. Therefore, in cases where you wish to display the URL because it is intrinsically valuable information, it is better to use the short form of the URL (host name) as the optional text:  produces example.org.

Link titles
You should not add a descriptive title to an embedded HTML link within an article. Instead, when giving an embedded link as a source within an article, simply enclose the URL in square brackets, like this:  →. However, you should add a descriptive title when an external link is offered in the References, Further reading, or External links section. This is done by supplying descriptive text after the URL, separated by a space and enclosing it all in square brackets.

For example, to add a title to a bare URL such as  (this is rendered as http://en.wikipedia.org/), use the following syntax:   (this is rendered as "an open-content encyclopedia").

Generally, URLs are ugly and uninformative; it is better for a meaningful title to be displayed rather than the URL itself. For example, European Space Agency website is much more reader-friendly than http://www.esa.int/export/esaCP/index.html. There may be exceptions where the URL is well known or is the company name. In this case, putting both the URL and a valid title will be more informative: for example, European Space Agency website, www.esa.int.

If the URL is displayed, make it as simple as possible; for example, if the  is superfluous, remove it (but be sure to check in preview mode first).

The "printable version" of a page displays all URLs in full, including those given a title, so no information is lost.

URLs as embedded (numbered) links
Without the optional text, external references appear as automatically numbered links: For example,

is displayed like this:
 * 

When an embedded HTML link is used to provide an inline source in an article, a numbered link should be used after the punctuation, like this, with a full citation given in the References section. This style of referencing is not recommended, because such links are susceptible to link rot. See Cite sources and Verifiability for more information.

When placed in the References and External links sections, these links should be expanded with link text, and preferably a full citation, including the name of the article, the author, the journal or newspaper the article appeared in, the date it was published, and the date retrieved.

Position in article
Embedded links that are used to support information in an article are positioned in the same manner as any other reference in the article, following the usual standards about citation formatting and placement in relation to punctuation.

Links that are not used as sources can be listed in the External links section, like this:



As with other top-level headings, two equal signs should be used to mark up the external links heading (see Headings elsewhere in the article). External links should always be the last section in an article. It precedes categories and some kinds of navigation templates.

If there is a dispute on the position of an embedded link, consider organizing alphabetically.

Non-English-language sites
Webpages in English are highly preferred. Linking to non-English pages may still be useful for readers in the following cases:
 * when the website is the subject of the article
 * when linking to pages with maps, diagrams, photos, tables (explain the key terms with the link, so that people who do not know the language can interpret them)
 * when the webpage contains information found on no English-language site of comparable quality, and is used as a citation (or when translations on English-language sites are not authoritative).

If the language is one that most readers could not be expected to recognize, or is for some other reason unclear from the name of the publication or the book/article/page title, consider indicating what language the site is in.
 * Example: El País, a Spanish-language newspaper from Madrid

You can also indicate the language by putting a language icon after the link. This is done using Template:Language icon by typing. For example,  displays as:. Alternatively, type, where   is the language code. For example,  gives:. See Category:Language icon templates for a list of these templates and the list of ISO 639 codes.

File type and size
If the link is not to an HTML or PDF file (the latter is identified automatically by the software with an icon like this: ), identify the file type. Useful templates are available: DOClink, RTFlink. If a browser plugin is required to view the file, mention that as well. If a link is to a PDF file but doesn't end with, you can put a   at the end to flag it as a PDF.

If the link is to a large file (in the case of HTML, consider the size of the entire page, including the images), a note about that is useful too. Someone with a slow (or expensive) connection may decide not to use it.

Linking
Interwiki links can take the form of:
 * which appears as: article

The pipe symbol suppresses the prefix:
 * → article

Adding text after the pipe allows different text:
 * → Any text

Floating boxes
Floating boxes for links to articles in other Wikimedia Foundation projects such as Wiktionary and Wikiquote can be done with special link templates such as. These will display as a box with a logo. Similar templates exist for some free content resources that are not run by the Wikimedia Foundation. These boxes are formatted in light green to distinguish them from Wikipedia's official sister projects. A list of such templates can be found at List of templates linking to other free content projects.

Link maintenance
Linking and continual change are both central features of Wikipedia. However, continual change makes linking vulnerable to acquired technical faults, and to the later provision of different information from that which was originally intended. This is true of both "outgoing" links (from an article) and "incoming" links (to an article).
 * Outgoing links: These should be checked from time to time for unintended changes that are undesirable. If the opportunity arises to improve their formatting, appropriateness, and focus, this should be done.
 * Incoming links: Creating an article will turn blue any existing red links to its title (proper redlinks are created only in the hope that an article will eventually be written). Therefore, when creating an article, it is wise to check "What links here" to identify such redlinks, if any, and that they are appropriate.