Editing Link rot (section)

== Causes ==
Link rot can result for several reasons. A target web page may be removed. The server that hosts the target page could fail, be removed from service, or relocate to a new [[domain name]]. As far back as 1999, it was noted that with the amount of material that can be stored on a hard drive, "a single disk failure could be like the burning of the [[Library of Alexandria|library at Alexandria]]."<ref name="McGranaghan1999">{{cite journal |last1=McGranaghan |first1=Matthew |date=1999 |title=The Web, Cartography and Trust |url=https://cartographicperspectives.org/index.php/journal/article/view/cp32-mcgranaghan |journal=Cartographic Perspectives |volume= |issue=32 |pages=3–5 |doi=10.14714/CP32.624 |doi-access=free|url-access=subscription }}</ref>  A domain name's registration may lapse or be transferred to another party. Some causes will result in the link failing to find any target and returning an error such as [[HTTP 404]]. Other causes will cause a link to target content other than what was intended by the link's author.

Other reasons for broken links include:
* the restructuring of websites that causes changes in URLs (e.g. {{code|domain.net/pine_tree}} might be moved to {{code|domain.net/tree/pine}})
* relocation of formerly free content to behind a [[paywall]]<ref name="Adams1" />
* a change in server architecture that results in code such as [[PHP]] functioning differently
* dynamic page content such as search results that changes by design
* deletion of the target page and/or its content
* the presence of user-specific information (such as a login name) within the link
* deliberate blocking by [[content filter]]s or [[Firewall (networking)|firewalls]]
* the expiration of a [[domain name registration]]