Concept and specification
– The ‘nofollow’ value was suggested to combat comment spam in blogs.
– It was proposed by Google’s Matt Cutts and Blogger’s Jason Shellen in 2005.
– The specification for ‘nofollow’ is copyrighted 2005-07 by the authors.
– The value is subject to a royalty-free patent policy per the W3C Patent Policy.
– It is also subject to IETF RFC 3667 & RFC 3668.
Example and support
– An example of a ‘nofollow’ link is: Link text.
– Google announced in 2005 that ‘nofollow’ links would not influence PageRank.
– Yahoo and Bing search engines also respect the ‘nofollow’ attribute.
– In 2009, GoogleBot changed the way it treats ‘nofollow’ links to prevent PageRank sculpting.
– As of March 2020, Google treats the ‘nofollow’ attribute as a hint for crawling and indexing.
– The usage of ‘nofollow’ affects the distribution of PageRank among links.
Interpretation by the individual search engines
– Different search engines interpret ‘nofollow’ differently.
– Google takes ‘nofollow’ literally and does not follow the link.
– Yahoo! and Bing exclude ‘nofollow’ links from their ranking calculation.
– Ask.com and Baidu also respect the ‘nofollow’ attribute.
– The exact interpretation may vary between search engines.
Use on other websites
– MediaWiki software, used by Wikipedia, implemented ‘nofollow’ support in 2005.
– Initially, the English Wikipedia used a URL blacklist instead of ‘nofollow’ in articles.
– In 2007, ‘nofollow’ was added to article-space links on the English Wikipedia.
– Other Wikimedia Foundation projects and external wikis are not affected by this policy.
– Websites like Slashdot and social bookmarking sites use ‘nofollow’ selectively for user-submitted links.
Qualified outbound links and related topics
– Google introduced two ways to qualify outbound hyperlinks: rel=sponsored and rel=ugc.
– rel=sponsored is used for links that are advertisements, sponsorships, or compensation agreements.
– rel=ugc is used for user-generated content like comments and forum posts.
– The attributes can be combined, such as rel=ugc sponsored.
– WordPress plans to convert all blog comments into rel=ugc.
– See also: noindex, PageRank, search engine optimization, web crawlers (search engine spiders), spam in blogs about nofollow, link building, blocking and excluding content from search engines (robots meta tag, robots exclusion standard – robots.txt).
References:
– The nofollow Attribute and SEO, archived from the original on 2011-07-15
– rel=nofollow Specification, Microformats.org, retrieved June 17, 2007
– W3C Patent Policy 20040205, W3.ORG
– HTML 4.01 Specification, W3C.org, retrieved May 29, 2007
– Preventing comment spam, Official Google Blog, retrieved on May 29, 2007
Additional information:
– Use rel=nofollow for specific links – Search Console Help
– How Google, Yahoo & Ask.com Treat the No Follow Link Attribute – Search Engine Journal
– Dofollow And Nofollow Links In SEO – Beta Compression
– Webmasters. About Ask.com
– Google Blog, Preventing comment spam – The Official Google Blog
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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 website authors to indicate that the presence of a link is not an endorsement of the target site's importance.
