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nofollow is a setting on a web page hyperlink that directs search engines not to use the link for page ranking calculations. It is specified in the page as a type of link relation; that is:
<a rel="nofollow" ...>. Because search engines often calculate a site's importance according to the number of hyperlinks from other sites, the
nofollow setting allows web site authors to indicate that the presence of a link is not an endorsement of the target site's importance.
Concept and specification
nofollow value was originally suggested to stop comment spam in blogs. Believing that comment spam affected the entire blogging community, in early 2005 Google's Matt Cutts and Blogger's Jason Shellen proposed the value to address the problem.
<a href="http://www.example.com/" rel="nofollow">Link text</a>
Introduction and support
Google announced in early 2005 that hyperlinks with
rel="nofollow" would not influence the link target's PageRank. In addition, the Yahoo and Bing search engines also respect this attribute value.
On June 15, 2009, Google software engineer Matt Cutts announced on his blog that GoogleBot changed the way it treats nofollowed links, in order to prevent webmasters from using nofollow for PageRank sculpting. Prior to this, webmasters would place nofollow tags on some of their links in order to maximize the PageRank of the other pages. As a result of this change, the usage of nofollow leads to evaporation of pagerank of outgoing normal links as they started counting total links while calculating page rank. The new system divides page rank by total number of outgoing links irrespective of nofollow or follow links, but passes the page rank only through follow or normal links. Cutts explained that if a page has 5 normal links and 5 nofollow outgoing links, the page rank will be divided by 10 links and one share is passed by 5 normal links. However, as of March 1 2020, Google is treating the nofollow link attribute as a hint, rather than a directive, for crawling and indexing purposes.
Interpretation by the individual search engines
While all engines that use the
nofollow value exclude links that use it from their ranking calculation, the details about the exact interpretation of it vary from search engine to search engine.
- Google states that their engine "in general" takes "nofollow" literally and does not "follow" the link.
- Yahoo! follows it, but excludes it from their ranking calculation.
- Bing may not follow it, but excludes it from their ranking calculation.
- Ask.com also respects the attribute.
- Baidu appears to respect the attribute.
|Uses the link for ranking||No||No||No||N/A||No|
|Follows the link||No||Yes||N/A||No||N/A|
|Indexes the "linked to" page||No||Yes||No||No||N/A|
|Shows the existence of the link||Only for a previously indexed page||Yes||Yes||Yes||N/A|
|In results pages for anchor text||Only for a previously indexed page||Yes||Only for a previously indexed page||Yes||N/A|
Use by weblog software
Many weblog software packages mark reader-submitted links this way by default (often with no option to disable it, except for modification of the software's code).
More sophisticated server software could suppress the nofollow for links submitted by trusted users like those registered for a long time, on a whitelist, or with an acceptable karma level. Some server software adds
rel="nofollow" to pages that have been recently edited but omits it from stable pages, under the theory that stable pages will have had offending links removed by human editors.
The widely used blogging platform WordPress versions 1.5 and above automatically assign the
nofollow attribute to all user-submitted links (comment data, commenter URI, etc.). However, there are several free plugins available that automatically remove the
nofollow attribute value.
Use on other websites
This article's factual accuracy may be compromised due to out-of-date information. (November 2010)
MediaWiki software, which powers Wikipedia, was equipped with nofollow support soon after the initial announcement in 2005. The option was enabled on most Wikipedias. One of the prominent exceptions was the English Wikipedia. Initially, after a discussion, it was decided not to use
rel="nofollow" in articles and to use a URL blacklist instead. In this way, the English Wikipedia contributed to the scores of the pages it linked to, and expected editors to link to relevant pages.
In May 2006, a patch to MediaWiki software allowed enabling nofollow selectively in namespaces. This functionality was used on pages that are not considered to be part of the actual encyclopedia, such as discussion pages, user pages and resources for editors.
Following increasing spam problems and a within-Foundation request from co-founder Jimmy Wales,
rel="nofollow" was added to article-space links in January 2007. However, the various interwiki templates and shortcuts that link to other Wikimedia Foundation projects and many external wikis such as Wikia are not affected by this policy.
Other websites like Slashdot, with high user participation, add
rel="nofollow" only for potentially misbehaving users. Potential spammers posing as users can be determined through various heuristics like age of registered account and other factors. Slashdot also uses the poster's karma as a determinant in attaching a nofollow tag to user-submitted links.
Social bookmarking and photo sharing websites that use the
rel="nofollow" tag for their outgoing links include YouTube and Digg.com (for most links); websites that don't use the
rel="nofollow" tag include Yahoo! My Web 2.0, Technorati Favs, and Propeller.com (no longer an active website).
Search engines have attempted to repurpose the nofollow attribute for something different. Google began suggesting the use of
nofollow also as a machine-readable disclosure for paid links, so that these links do not get credit in search engines' results. Google considers paid backlinks a black-hat practice. When it comes to link building strategy, getting organic links is the right way of doing it. Paid links do not assure high authority links from sources relevant to a niche market or industry. Moreover, paid links are mostly considered as spam links which might be lost after a long period of time. Also, this kind of linking practice might not generate high traffic and also does not build brand identity.
The growth of the link buying economy, where companies' entire business models are based on paid links that affect search engine rankings, caused the debate about the use of
nofollow on paid links to move into the center of attention of the search engines, who started to take active steps against link buyers and sellers. This triggered a very strong response from web masters.
Control internal PageRank flow
Search engine optimization professionals started using the
nofollow attribute to control the flow of PageRank within a website, but Google has since corrected this error, and any link with a nofollow attribute decreases the PageRank that the page can pass on. This practice is known as "PageRank sculpting". This is an entirely different use than originally intended.
nofollow was designed to control the flow of PageRank from one website to another. However, some SEOs have suggested that a
nofollow used for an internal link should work just like
nofollow used for external links.
nofollow on internal links pointing to them. Google employee Matt Cutts has provided indirect responses on the subject, but has never publicly endorsed this point of view.
The practice is controversial and has been challenged by some SEO professionals, including Shari Thurow and Adam Audette. Site search proponents have pointed out that visitors do search for these types of pages, so using
nofollow on internal links pointing to them may make it difficult or impossible for visitors to find these pages in site searches powered by major search engines.
Although proponents of use of
nofollow on internal links have cited an inappropriate attribution to Matt Cutts (see Matt's clarifying comment, rebutting the attributed statement) as support for using the technique, Cutts himself never actually endorsed the idea. Several Google employees (including Matt Cutts) have urged Webmasters not to focus on manipulating internal PageRank. Google employee Adam Lasnik has advised webmasters that there are better ways (e.g. click hierarchy) than
nofollow to "sculpt a bit of PageRank", but that it is available and "we're not going to frown upon it".
Use of nofollow where comments or other user content is posted (such as Wikipedia) not only depreciates the links of spammers but also of users that might be constructively contributing to a discussion and preventing such legitimate links from influencing the page ranking of the websites they target.
Criticism of usage by Wikipedia
Employment of the nofollow attribute by Wikipedia on all external links has been criticized by web authors for not passing the deserved rank to referenced pages which serve as the original source of each Wikipedia article's content. The decision was enacted on Wikipedia to combat spamdexing on its pages, which are an otherwise tempting target for spammers as Wikipedia is a very high-ranking site on most search engines. The drawbacks for original publishers are that they must compete with the Wikipedia article for a higher rank in search results and that their website does not receive the increase in rank that otherwise would have been contributed without nofollow.
On September 10, 2019, Google announced two additional ways for webmasters to qualify the relationship of outbound hyperlinks. The attribute
rel="sponsored" may be used to denote links that are advertisements, sponsorships or other compensation agreements. The attribute
rel="ugc", standing for "User-Generated Content", may be used to denote content such as user-contributed comments and forum posts. Additionally, the attributes may be combined, such as
rel="ugc sponsored", denoting a link that was both user-generated and sponsored.
In 2019, WordPress announced plans to convert all blog comments into rel="ugc".
These "hint" link attributes address some of the criticisms of
nofollow by allowing webmasters to denote outbound links that lack "the weight of a first-party endorsement", but are not necessarily spam.
- Search engine optimization
- Web crawlers, also called Search engine spiders
- Spam in blogs about nofollow
Blocking and excluding content from search engines
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