Is thesaurus.net Safe?

It won't let me view any synonyms with adblock enabled. It asks me to turn off adblock or pay $0.99/month to continue with adblock enabled. It is very suspicious that a website wants to charge you just because you have a browser extension installed. We use adblock because of malicious ads. The fact that a website wants you to disable your adblocker or pay to use a website that is free in order to continue using adblock on the website says that there is something going on with their ads that they are dying to show people. There are many free websites that don't do this. I would not go here.