Help:External links

Often there is a need to add references, citations, or further reading links to a wiki page. When these links are external to wiki.gis.com, it becomes necessary to add specific code to insert these external links into the wiki page.

This page will provide you with the technical method for creating these external links.

But first a note of caution: while some external links on a wiki page are welcome, it is not wiki.gis.com's purpose to become a comprehensive list of external links related to each topic. No page should be linked from a wiki.gis.com page unless its inclusion is justifiable.

If the Web site or page to which you want to link includes information that is not yet a part of your wiki page, consider using it as a source for the article, and citing it. Guidelines for sourcing, which includes external links used as citations, are discussed at Help:Citing sources.

Important points to remember

 * 1) External links should not normally be used in the body of a wiki page. Instead, include appropriate external links in an "External links" section at the end of the wiki page.
 * 2) Links in the "External links" section should be relevant to the wiki page from which they are linked. A lack of external links or a small number of external links is not a reason to add external links.
 * 3) In the "External links" section, try to avoid separate links to multiple pages in the same Web site; instead, try to find an appropriate linking page within the site.
 * 4) These guidelines for external links do not apply to inline citation or general references, which should appear in the "References" or "Notes" section.

Restrictions on linking
For policy or technical reasons, editors are restricted from linking to the following, without exception:
 * 1) Material that violates the copyrights of others per contributors' rights and obligations should not be linked. Linking to Web sites that display copyrighted works is acceptable as long as the Web site has licensed the work. Knowingly directing others to material that violates copyright may be considered contributory copyright infringement. If you know that an external Web site is carrying a work in violation of the creator's copyright, do not link to that copy of the work. Linking to a page that illegally distributes someone else's work sheds a bad light on Wiki.gis.com and its editors. This is particularly relevant when linking to sites such as YouTube, where due care should be taken to avoid linking to material that violates its creator's copyright.
 * 2) Sites that match the Wiki.gis.com or multi-site spam blacklist without being whitelisted. MediaWiki's code will automatically block any edits that contain such links.

What to link
There are several things that should be considered when adding an external link.
 * Is the site content accessible to the reader?
 * Is the site content proper in the context of the article (useful, tasteful, informative, factual, etc.)?
 * Is the link functional and likely to remain functional?

Each link should be considered on its merits, using the following guidelines. As the number of external links in a wiki page grows longer, assessment should become stricter. When in doubt about the appropriateness of adding new links, make a suggestion on the wiki page's talkpage and discuss with other editors.

What should be linked

 * 1) Wiki.gis.com pages about an organization, person, Web site, or other entity should link to the subject's official site, if any.
 * 2) A wiki page about a book, a particular script, piece of code or resource being used via the Resource Centers, or some other media should link to the site hosting that copy of the work, if none of the copyright or blacklisted guidelines or criteria apply.
 * 3) Sites that contain neutral and accurate material that cannot be integrated into the wiki.gis.com page due to copyright issues, amount of detail (such as interview transcripts or online textbooks), or other reasons.

Links that should normally be avoided
Beyond what was stated above, one should avoid:
 * 1) Sites that are only indirectly related to the article's subject: the link should be directly related to the subject of the article. A general site that has information about a variety of subjects should usually not be linked to or from a wiki page on a more specific subject. Similarly, a Web site on a specific subject should usually not be linked from an article about a general subject. If a section of a general Web site is devoted to the subject of the article, and meets the other criteria for linking, then that part of the site could be deep linked, meaning to make a hyperlink that points to a specific page or image on another Web site, instead of that Web site's main or home page.
 * 2) Lists of links to manufacturers, suppliers or customers.
 * 3) Links that are not reliably functional, or likely to continue being functional. For example, links to temporary internet content, where the link is unlikely to remain operable for a useful amount of time.
 * 4) Placing external links on wiki.gis.com navigation pages such as disambiguation, redirect and category.
 * 5) Any site that does not provide a unique resource beyond what the page would contain if it became Featured content.
 * 6) Any site that misleads the reader by use of factually inaccurate material or unverifiable research, except to a limited extent in articles about the viewpoints which such sites are presenting.
 * 7) Any site that attempts to surreptitiously install malware onto a visitor's computer.
 * 8) Links mainly intended to promote a Web site.
 * 9) Links to Web pages that primarily exist to sell products or services, or to Web pages with objectionable amounts of advertising.
 * 10) Links to sites that require payment or registration to view the relevant content, unless the site itself is the subject of the content.
 * 11) Sites that are inaccessible to a substantial number of users, such as sites that only work on a specific browser or in a specific country.
 * 12) Direct links to documents that require external applications (such as Flash or Java) to view the relevant content. If you do link to such material make note of what application is required.
 * 13) Links to any search results pages, such as links to individual Web site searches, search engines, search aggregators, or RSS feeds.
 * 14) Links to social networking sites (such as MySpace and Facebook), chat or discussion forums/groups (such as GIS Lounge - GIS Forums), Twitter feeds, USENET newsgroups or e-mail lists.
 * 15) Links to blogs, personal Web pages, and most fan sites, except those written by a recognized authority. (If in doubt, share the link with the wiki community using the Discussion room).
 * 16) Links to open wikis, except those with a substantial history of stability and a substantial number of editors (such as Wikipedia).