 | This is an information page. It is not an encyclopedic article, nor one of Wikipedia's policies or guidelines; rather, its purpose is to explain certain aspects of Wikipedia's norms, customs, technicalities, or practices. It may reflect differing levels of consensus and vetting. |
 | This page in a nutshell: The community has decided to exclude certain highly questionable sources from articles, except in special cases. |
Deprecated sources are highly questionable sources that editors are discouraged from citing in articles, because they fail the reliable sources guideline in nearly all circumstances. Use of these sources may generate edit filter warnings for registered users and may be automatically reverted for edits from IP addresses.
Deprecation is a formalization that arises from Wikipedia’s normal processes for evaluating sources. It primarily exists to save time by avoiding the endless discussion of the same issues, and to raise awareness among editors of the status of the sources in question. For example, if editors are unfamiliar with either the specific sources or the general sourcing requirements, they can be saved the experience of having their work undone later on. Deprecation can be proposed with a request for comment at the reliable sources noticeboard, and the restrictions are only applied if there is community consensus.[1]
Since there are an endless number of poor sources, there are also an endless number of sources that would be deprecated if we bothered to have discussions on them. These sources have always been de facto deprecated as a normal result of our policies and guidelines that try to ensure that we use reputable sources. A discussion that results in deprecation may involve a change or clarification of editorial consensus (thus resulting in a change of current practice), but the only effect of deprecation alone is to explicitly codify the source’s pre-existing status, as already determined by Wikipedia’s sourcing requirements. It does not inherently change how they are evaluated under those requirements.
Deprecated sources should not be considered to be either unique or uniquely unreliable. They may be those that are most often cited by unaware editors, or those that come up in discussion the most often – for example, due to real-world controversy, borderline reliability, or a tendency to be promoted on-wiki despite a lack of reliability. Since there are many reasons that a source may be unreliable, the specific reasons for deprecation vary from case to case. The first source to be formally deprecated was the Daily Mail, which was determined by community consensus in a 2017 RfC to have a "reputation for poor fact checking, sensationalism, and flat-out fabrication". This RfC became a landmark decision, and new deprecation proposals are usually based on language from its closing summary.
Deprecating a source is different from blocking the source (blacklisting), which is generally done to address spam-related issues.