Whether or not they are "allowed" (and for this, I would ask your Supervisor / check your university guidelines) the bigger question is whether or not they are reliable.
Who is behind the website?
Does the website have a political leaning or agenda or other kind of bias?
Fact-checking websites should therefore be used with a critical eye .
So if you're going to use one, do the research to find one that has established credibility.
If overused, they might also smack of corner-cutting - that the student can't be bothered to do the donkey work in tracking valid and reliable published sources for their factual information.