Ahrefs

Ahrefs is a search engine data tool. With Ahrefs you gain insight into how well a website scores in the search results of Google. Ahrefs offers insight into external backlinks, content analysis, a competition analysis, positions in search engines and other SEO-related data. 

Ahrefs is widely used within online marketing and distinguishes itself from Semrush and Moz by its large database of backlinks. With the data that you get from Ahrefs, you can make a website better findable in search engines. With Ahrefs you can also see how your competitors score on keywords and qualitative link building. Based on this information, you can improve your own website in order to stay ahead of the competition. 

Other search engine data tools are for instance Moz and Semrush.