You can use the Monitor Backlinks Free Backlink Checker tool to check any website's Trust Flow—and thus if it's likely a seed site. You can also see the TF of any added competitor. For example, I found that Facebook has a near-perfect TF, meaning it's likely a seed site.

What is Domain Authority and why is it important? Domain Authority (DA) is a search engine ranking score developed by Moz that predicts how likely a website is to rank in search engine result pages (SERPs). Domain Authority scores range from one to 100, with higher scores corresponding to greater likelihood of ranking.

Domain Authority (DA) is a score developed by Moz that predicts how likely a website is to rank well. Moz DA ranges from 1 to 100, with higher scores equalling a better domain (aka a better chance of ranking highly). DA is calculated by evaluating multiple factors such as the number of backlinks pointing to a domain.

Use a browser extension such as MozBar or Ahrefs: This extension, which is available for Chrome and Firefox, displays the PA score of the webpage you are currently viewing along with other information such as Domain Authority (DA) and the number of inbound links.