No-follow and do-follow are all about additions to hyperlinks. A do-follow link is simply a regular hyperlink that may or may not have anchor text or an anchor image or video. A no-follow link has a small piece of code that stops search engines from crawling the link. The use of no-follow code is currently most common in WordPress comment sections. As a default the no-follow code is used on WordPress comment sections to lower the chances of people spamming links onto the comment section.
If the link inserted into a comment section is not going to be crawled by the search engine (not going to be followed) then there is no point in spamming a link to the comment section. Since WordPress powers one out of every six websites, it seems as if this default function has been effective in lowering the amount of spam links within comment sections.
Why would you want to check for the no-follow code?
To gain an SEO (Search Engine Optimization) benefit from a backlink it will need to be crawled. In other words it will need to be followed, and if a website is predominantly adding no-follow backlinks then no SEO benefit may be gained from that website.
If you are looking to install followed backlinks onto a website, then it may be a good idea to check to see if the website in question is accepting followed backlinks. If for example, you were looking to install a link into a comment section, then you may use a tool to check to see if the current links are being followed. If none of them are then you may decide against putting a backlink into the comment section.
This is not the only use for a tool that checks for no-follow code, but it is the predominant use of such a tool. Here are a few you may wish to try.
This is Chrome plugin that you may use to find the No-follow code. When you install the plugin you will see an icon appear in the top right corner. Open up a page you want to check and click on the icon. It will show you links in two colors. It will show you ones in green and ones in red.
This only works for HTML links and not for other types of links. The ones in green are the ones that are followed, and the ones in red are the ones with the no-follow code attached. You should expect to see internal links in green. If there are links installed on the comment section and they are red then there is little point in you putting your link on that comment section. The developers have released a version that works for Firefox too.
These is a Firefox plugin and it will show you things that relate to your SEO. The ones that stand out the most are the PageRank and Alexa Rank. You are able to see the backlinks that are pointing at your website too. If you want to see which links on a page are followed and which are not then go to the right hand corner and click on the icon. It will show you which links are followed and which are not.
This is a Firefox plugin. The plugin may be used to highlight all of the links to show which are followed and which are not. When the plugin is installed you will need to go to the tools section and click the NoDoFollow button. Or, you may right click on the page and pick NoDoFollow from the menu that drops down. The links that are followed will appear as blue and the ones that are not followed will appear as red.
It is better to use software to figure out if links are followed or not. The only other methods for checking if links are no-follow is to either check the source code yourself and look for the no-follow code, or to do a little trial and error linking and see with backlinks appear on your backlink reports.
Finding the no-follow code within the source code is quite easy as all you have to do is search for it with the browser search function. Though, it is rather a bit easier to have a plugin piece of software do the work for you. It saves you the inconvenience of opening up and looking through source code, especially if the website happens to have a lot of links on it.