The website says all blogs/website were ranked based on following criteria:
- Google reputation and Google search ranking
- Influence and popularity on Facebook, Twitter, and other social media sites
- Quality and consistency of posts
- Feedspot’s editorial team and expert review
You can see the full list here.
Feedspot describes itself as a website that "helps you keep track of all your favorite blogs, news sites and rss feeds in one place. It makes checking your favorite sites as easy as checking your emails."