relnofollow
Rel=nofollow is an HTML attribute value applied to hyperlinks. When a link includes rel="nofollow," it signals to search engines that the linking page does not endorse the target and that PageRank or other ranking signals should not be passed through that link. It is an instruction, not a strict prohibition; search engines may still crawl or index the linked page for purposes of discovery or other signals.
Origin and purpose: Introduced by Google in 2005 to combat spam and link manipulation on blogs and
Current practice and evolution: In 2019–2020, Google reframed nofollow as a hint for crawling and indexing rather
Usage notes: In practice, nofollow is commonly applied to blog comments, forums, and other user-generated content