The DoFollow link term was introduced by Google in 2015 to reduce search engine spam and improve the list of results. DoFollow links allow search engines and people to reach a website.
The dofollow links can be considered as votes for the authority of your website. For example, if you receive a dofollow backlink from a site with high authority, your site will be considered trustworthy and will further improve its authority.
If you want to check or identify a DoFollow link, you only need HTML.