Dofollow and nofollow are two types of HTML link attributes that provide instructions to search engine crawlers on how to treat those links when indexing web pages. Here's the difference between the two:

Dofollow Links

Dofollow links are standard HTML links that allow search engine crawlers to follow them and pass link authority (also known as link juice) from the referring webpage to the linked webpage. 

Dofollow Links

These links are considered by search engines when calculating rankings and can contribute to improving the visibility and organic search performance of the linked webpage. By default, all regular HTML links are dofollow unless specified otherwise.

Nofollow Links

Nofollow links, on the other hand, contain a rel="nofollow" attribute in their HTML code. This attribute instructs search engine crawlers not to follow the link or pass any link authority from the referring webpage to the linked webpage. 

Nofollow Links

Nofollow links were introduced to combat spam and to provide webmasters with a way to indicate that they don't endorse or vouch for the linked content. These links do not directly contribute to the search engine rankings of the linked webpage.

The rel="nofollow" attribute was originally introduced by major search engines to control the flow of link authority and combat link spam. 

However, it's important to note that search engines may still crawl and index the content of the linked webpage, even though they don't consider nofollow links for ranking purposes.

It's common to use nofollow links in certain scenarios, such as

User-generated content: When users contribute content to a website (such as blog comments or forum posts), using nofollow links helps prevent spam and external manipulation of search rankings.

Paid links and advertisements

When including sponsored links or paid advertisements on a webpage, nofollow attributes should be used to ensure compliance with search engine guidelines.

Untrusted or unverified links

When linking to external websites that are untrusted or haven't been verified for quality, using nofollow links can provide an additional layer of protection.

In summary, do follow links allow search engines to follow and pass link authority, influencing search rankings, while nofollow links instruct search engines not to follow the link or pass link authority.